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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2018	May 01, 2018
Document and Entity Information
Entity Registrant Name	AXCELIS TECHNOLOGIES INC
Entity Central Index Key	0001113232
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		32,145,565
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue	$ 122,185	$ 86,893
Cost of revenue:
Cost of revenue	75,029	52,179
Gross profit	47,156	34,714
Operating expenses:
Research and development	12,233	9,895
Sales and marketing	8,411	7,049
General and administrative	8,010	7,057
Total operating expenses	28,654	24,001
Income from operations	18,502	10,713
Other (expense) income:
Interest income	410	69
Interest expense	(1,337)	(1,111)
Other, net	(102)	(154)
Total other expense	(1,029)	(1,196)
Income before income taxes	17,473	9,517
Income tax provision	3,558	11
Net income	$ 13,915	$ 9,506
Net income per share:
Basic (in dollars per share)	$ 0.43	$ 0.32
Diluted (in dollars per share)	$ 0.41	$ 0.29
Shares used in computing net income per share:
Basic weighted average common shares	32,094	29,772
Diluted weighted average common shares	34,123	32,255
Product
Revenue	$ 116,022	$ 81,978
Cost of revenue:
Cost of revenue	68,374	46,797
Services
Revenue	6,163	4,915
Cost of revenue:
Cost of revenue	$ 6,655	$ 5,382

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Consolidated Statements of Comprehensive Income
Net income	$ 13,915	$ 9,506
Other comprehensive income:
Foreign currency translation adjustments	1,021	1,915
Amortization of actuarial loss and other adjustments from pension plan	30	28
Total other comprehensive income	1,051	1,943
Comprehensive income	$ 14,966	$ 11,449

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 140,957	$ 133,407
Short-term restricted cash	770	750
Accounts receivable, net	75,588	75,302
Inventories, net	135,005	120,544
Prepaid expenses and other current assets	9,277	9,772
Total current assets	361,597	339,775
Property, plant and equipment, net	36,203	36,168
Long-term restricted cash	6,744	6,723
Deferred income taxes	80,697	83,148
Other assets	19,903	22,404
Total assets	505,144	488,218
Current liabilities:
Accounts payable	43,438	32,642
Accrued compensation	7,685	20,955
Warranty	4,583	4,112
Income taxes	389	273
Deferred revenue	15,507	16,181
Other current liabilities	5,482	5,124
Total current liabilities	77,084	79,287
Sale leaseback obligation	47,724	47,714
Long-term deferred revenue	3,015	1,964
Other long-term liabilities	5,794	5,643
Total liabilities	133,617	134,608
Commitments and contingencies (Note 13)
Stockholders' equity:
Common stock, $0.001 par value, 75,000 shares authorized; 32,142 shares issued and outstanding at March 31, 2018; 32,048 shares issued and outstanding at December 31, 2017	32	32
Additional paid-in capital	557,498	556,147
Accumulated deficit	(189,230)	(204,745)
Accumulated other comprehensive income	3,227	2,176
Total stockholders' equity	371,527	353,610
Total liabilities and stockholders' equity	$ 505,144	$ 488,218

Consolidated Balance Sheets (Parenthetical) - $ / shares shares in Thousands	Mar. 31, 2018	Dec. 31, 2017
Consolidated Balance Sheets
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	75,000	75,000
Common stock, shares issued	32,142	32,048
Common stock, shares outstanding	32,142	32,048

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities
Net income	$ 13,915	$ 9,506
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	1,448	1,177
Deferred taxes	2,451	(22)
Stock-based compensation expense	1,132	1,075
Provision for excess and obsolete inventory	485	578
Changes in operating assets & liabilities:
Accounts receivable	16	(16,178)
Inventories	(11,462)	(844)
Prepaid expenses and other current assets	592	(2,347)
Accounts payable and other current liabilities	(1,836)	3,049
Deferred revenue	1,963	2,085
Income taxes	113	2
Other assets and liabilities	(317)	(749)
Net cash provided by (used in) operating activities	8,500	(2,668)
Cash flows from investing activities
Expenditures for property, plant and equipment and capitalized software	(723)	(1,116)
Net cash used in investing activities	(723)	(1,116)
Cash flows from financing activities
Net settlement on restricted stock grants	(226)	(286)
Proceeds from exercise of stock options	446	2,531
Net cash provided by financing activities	220	2,245
Effect of exchange rate changes on cash and cash equivalents	(406)	105
Net increase (decrease) in cash, cash equivalents and restricted cash	7,591	(1,434)
Cash, cash equivalents and restricted cash at beginning of period		140,880
Cash, cash equivalents and restricted cash at end of period	$ 148,471	$ 76,221

Nature of Business	3 Months Ended
Nature of Business	Mar. 31, 2018
Nature of Business
Nature of Business	Note 1. Nature of Business Axcelis Technologies, Inc. (“Axcelis” or the “Company”) was incorporated in Delaware in 1995, and is a producer of ion implantation and other processing equipment used in the fabrication of semiconductor chips in the United States, Europe and Asia. In addition, the Company provides extensive worldwide aftermarket service and support, including spare parts, equipment upgrades, used equipment and maintenance services to the semiconductor industry. The accompanying unaudited consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. In the opinion of management, all adjustments which are of a normal recurring nature and considered necessary for a fair presentation of these financial statements have been included. Operating results for the interim period presented are not necessarily indicative of the results that may be expected for other interim periods or for the year as a whole. The balance sheet at December 31, 2017 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. For further information, refer to the consolidated financial statements and footnotes thereto included in Axcelis Technologies, Inc.’s Annual Report on Form 10-K for the year ended December 31, 2017.

Stock-Based Compensation	3 Months Ended
Stock-Based Compensation	Mar. 31, 2018
Stock-Based Compensation
Stock-Based Compensation	Note 2. Stock-Based Compensation The Company maintains the Axcelis Technologies, Inc. 2012 Equity Incentive Plan (the “2012 Equity Plan”), which became effective on May 2, 2012, and permits the issuance of options, restricted stock, restricted stock units and performance awards to selected employees, directors and consultants of the Company. The Company’s 2000 Stock Plan (the “2000 Stock Plan”) expired on May 1, 2012 and no new grants may be made under that plan after that date. However, unexpired awards granted under the 2000 Stock Plan remain outstanding and subject to the terms of the 2000 Stock Plan. The Company also maintains the Axcelis Technologies, Inc. Employee Stock Purchase Plan (the “ESPP”), an Internal Revenue Code Section 423 plan. The 2012 Equity Plan and the ESPP are more fully described in Note 11 to the consolidated financial statements in the Company’s 2017 Annual Report on Form 10-K. The Company recognized stock-based compensation expense of $1.1 million for each of the three month periods ended March 31, 2018 and 2017 related to restricted stock units and non-qualified stock options. In the three month periods ended March 31, 2018 and 2017, the Company issued 0.1 million and 0.5 million shares of common stock, respectively, in relation to stock option exercises and vesting of restricted stock units. In the three month periods ended March 31, 2018 and 2017, the Company received proceeds of $0.4 million and $2.5 million, respectively, in connection with the exercise of stock options.

Revenue

3 Months Ended

Mar. 31, 2018

Revenue

Revenue

Note 3. Revenue

We design, manufacture and service ion implantation and other processing equipment used in the fabrication of semiconductor chips and sell our products to leading semiconductor chip manufacturers worldwide. We offer a complete line of high energy, high current and medium current implanters (“Systems”) for all application requirements. In addition, we provide extensive aftermarket lifecycle products and services (“Aftermarket”), including used tools, spare parts, equipment upgrades, maintenance service and customer training.

Under Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers or (“ASC 606”), revenue is recognized when a customer obtains control of promised goods or services in an amount that reflects the consideration we expect to receive in exchange for those goods or services. We measure revenue based on the consideration specified in the client arrangement, and revenue is recognized when the performance obligations in the client arrangement are satisfied. A performance obligation is a promise in a contract to transfer a distinct product or service to the customer. The transaction price of a contract is allocated to each distinct performance obligation based upon the relative standalone selling price for each performance obligation and recognized as revenue when or as, the customer receives the benefit of the performance obligation. See Footnote 14 regarding the impact of the adoption of ASC 606 on our financial statements. To achieve this core principle, the Company applies the following five steps:

Identify the contract with the customer

A contract with a customer exists when (i) the Company enters into an enforceable contract with a customer that defines each party’s rights regarding the goods or services to be transferred and identifies the related payment terms, (ii) the contract has commercial substance, and (iii) the Company determines that collection of substantially all consideration for goods and services that are transferred is probable based on the customer’s intent and ability to pay the promised consideration.

Identify the performance obligations in the contract

Performance obligations promised in a contract are identified based on the goods and services that will be transferred to the customer that are both capable of being distinct, whereby the customer can benefit from the good or service either on its own or together with other available resources, and are distinct in the context of the contract, whereby the transfer of the good or service is separately identifiable from other promises in the contract. To the extent a contract includes multiple promised goods and services, the Company must apply judgment to determine whether promised goods and services are capable of being distinct and distinct in the context of the contract. If these criteria are not met, the promised goods and services are accounted for as a combined performance obligation.

Our Systems sales consist of multiple performance obligations, including the system itself and obligations that are not delivered simultaneously with the system. These undelivered obligations might include a combination of installation services, extended warranty and support and spare parts, all of which are generally covered by a single sales price.

Our aftermarket business includes both products and services type arrangements. Performance obligations in these contracts consist of used tools, spare parts, equipment upgrades, maintenance services and customer training.

Customers who purchase new systems are provided an assurance-type warranty for one year after acceptance of the tool. For Aftermarket transactions, we provide customers an assurance-type warranty for 90 days. Customers can choose to purchase extended warranty terms with enhanced support similar to a service-type warranty ranging from one to three years. In accordance with ASC 606, assurance-type warranties are not considered a performance obligation, whereas service-type warranties are.

Determine the transaction price

The transaction price is determined based on the consideration to which the Company will be entitled in exchange for transferring goods and services to the customer. To the extent the transaction price includes variable consideration, the Company estimates the amount of variable consideration that should be included in the transaction price utilizing either the expected value method or the most likely amount method depending on the nature of the variable consideration. Variable consideration is included in the transaction price if, in the Company’s judgment, it is probable that a significant future reversal of cumulative revenue under the contract will not occur. Any estimates, including the effect of the constraint on variable consideration, are evaluated at each reporting period for any changes. In applying this guidance, Companies must also consider whether any significant financing components exist.

The transaction price for all transactions is based on the price reflected in the individual customers purchase order. Variable consideration has not been identified as a significant component of the transaction price for any of our transactions.

For those transactions where all performance obligations will be satisfied within one year or less, the Company is applying the practical expedient outlined in ASC 606-10-32-18. This practical expedient allows the Company not to adjust promised consideration for the effects of a significant financing component if the Company expects at contract inception the period between when the Company transfers the promised good or service to a customer and when the customer pays for that good or service will be one year or less. For those transactions that are expected to be completed after one year, the Company has assessed that there are no significant financing components because any difference between the promised consideration and the cash selling price of the good or service is for reasons other than the provision of financing.

Allocate the transaction price to performance obligations in the contract

If the contract contains a single performance obligation, the entire transaction price is allocated to the single performance obligation. Contracts that contain multiple performance obligations require an allocation of the transaction price to each performance obligation on a relative standalone selling price basis unless the transaction price is variable and meets the criteria to be allocated entirely to a performance obligation or to a distinct service that forms part of a single performance obligation.

Where required, the Company determines standalone selling price (SSP) for each obligation based on consideration of both market and Company specific factors, including the selling price and profit margin for similar products, the cost to produce, and the anticipated margin

For those contracts that contain multiple performance obligations (primarily systems sales, as well as some aftermarket contracts requiring both time and material inputs), the company must determine SSP. The Company used a cost plus margin approach in determining the SSP for any materials related performance obligations (such as upgrades, spare parts, systems). To determine the SSP for labor related performance obligations (such as the labor component of installation), the Company used directly observable inputs based on the standalone sale prices for these services.

Recognize revenue when or as the Company satisfied a performance obligation

The Company satisfies performance obligations either over time or at a point in time. Revenue is recognized over time if either 1) the customer simultaneously receives and consumes the benefits provided by the entity’s performance, 2) the entity’s performance creates or enhances an asset that the customer controls as the asset is created or enhanced, or 3) the entity’s performance does not create an asset with an alternative use to the entity and the entity has an enforceable right to payment for performance completed to date. If the entity does not satisfy a performance obligation over time, the related performance obligation is satisfied at a point in time by transferring the control of a promised good or service to a customer. Examples of control are using the asset to produce goods or services, enhance the value of other assets, settle liabilities, and holding or selling the asset. For over time recognition, ASC 606 requires the Company to select a single revenue recognition method for the performance obligation that faithfully depicts the Company’s performance in transferring control of the goods and services. The guidance allows entities to choose between two methods to measure progress toward complete satisfaction of a performance obligation:

Output methods - recognize revenue on the basis of direct measurements of the value to the customer of the goods or services transferred to date relative to the remaining goods or services promised under the contract (e.g. surveys of performance completed to date, appraisals of results achieved, milestones reached, time elapsed, and units of produced or units delivered); and

Input methods - recognize revenue on the basis of the entity’s efforts or inputs to the satisfaction of a performance obligation (e.g., resources consumed, labor hours expended, costs incurred, or time elapsed) relative to the total expected inputs to the satisfaction of that performance obligation.

The Company has the right to consideration from a customer in an amount that corresponds directly with the value to the customer of the entity’s performance completed to date (i.e. certain aftermarket contracts), as such the Company has elected a practical expedient to recognize revenue in the amount to which the entity has a right to invoice for such services.

Product related revenues (whether for systems or aftermarket business) are recognized at a point in time, when they are shipped or delivered, depending on shipping terms.

For installation services, revenue is recognized at a point in time, once the installation of the tool is complete. The nature of the installation services are such that the customer does not simultaneously receive and consume the benefits provided by the entity’s performance, nor does performance of installation services create or enhance an asset that the customer controls. Installation services do not create an asset with an alternative use to the entity, and the entity does not have an enforceable right to payment for performance completed to date.

Service-type warranties for any product are recognized over time, as these represent a stand ready obligation to service the product during the warranty period. Progress in the satisfaction of these performance obligations will be measured using an input method of time elapsed.

Maintenance and service contracts are recognized over time. Progress in the satisfaction of these performance obligations will be measured using an input method of either time elapsed in the case of fixed period contracts, or labor hours expended, in the case of project based contracts.

Cost to Obtain and Fulfill a Contract with a Customer

The Company recognizes an asset related to incremental costs of obtaining a contract with a customer if the Company expects to recover those costs. The Company will recognize an asset from costs incurred to fulfill a contract only if such costs relate directly to a contract that the entity can specifically identify, the costs generate or enhance resources of the Company that will be used in satisfying performance obligations in the future, and the costs are expected to be recovered. Any assets recognized related to costs to obtain or fulfill a contract are amortized on a systematic basis that is consistent with the transfer to the customer of the goods or services to which the asset relates.

In substantially all of our business transactions, we incur incremental costs to obtain contracts with customers, in the form of sales commissions. We maintain a commission program which awards our employees for System sales, aftermarket activity and other individual goals. Under ASC 606, an asset shall be amortized on a systematic basis that is consistent with the transfer to the customer of the goods or services to which the asset relates. However, ASC 606 provides a practical expedient to allow for the recognition of commission expense when incurred if the amortization period of the asset that the entity otherwise would have recognized is one year or less. Based on the nature of the Company’s commission agreements, all commissions are expensed as incurred based upon the expectation that the amortization period would be one year or less.

Revenue Categories used by Management

Our business operates in the following fundamental disciplines: Systems and Aftermarket.

Revenue by categories used by management are as follows:


	Three months ended
	March 31,
	2018*		2017
	(in thousands)
Systems	$	85,475	$	55,249
Aftermarket		36,710		31,644
	$	122,185	$	86,893

*The impact upon adoption of ASC 606 was an increase to Systems revenue of $1.0 million.

The increase in revenue in the three months ended March 31, 2018, in comparison to the three months ended March 31, 2017, is attributable to an increase in sales of our Purion products.

Economic factors affecting our revenue

Global economic conditions have a direct impact on our revenue. We are substantially dependent on sales of our products and services to customers outside the United States. Adverse economic conditions such as political and economic instability, potential adverse tax consequences and volatility in exchange rates pose a risk that our clients may reduce, postpone or cancel spending for our products and services, which would impact our revenue.

Revenue by geographic markets is determined based upon the location of where our products are shipped and our services are performed. Revenue in our principal geographic markets is as follows:


	Three months ended
	March 31,
	2018*		2017
	(in thousands)
North America	$	10,523	$	6,997
Asia		97,689		63,245
Europe		13,973		16,651
	$	122,185	$	86,893

*The impact upon adoption of ASC 606 was an increase in revenue to Asia of $1.5 million and decreases of $0.3 million and $0.2 million to North America and Europe, respectively.

Contract assets and liabilities

Contract assets and contract liabilities are as follows:


	March 31,		December 31,		March 31,
	2018		2017		2017
	(in thousands)
Contract assets	$	—	$	—	$	—

Contract liabilities	$	18,522	$	18,145	$	13,121

Revenue recognized in the period from:
Amounts included in contract liability at the beginning of the period	$	6,342	$	9,105	$	5,277
Performance obligations satisfied in previous periods	$	—	$	—	$	—

Contract liabilities are reflected as deferred revenue on the consolidated balance sheet. Contract liabilities relate to payments invoiced or received in advance of completion of performance obligations under a contract. Contract liabilities are recognized as revenue upon the fulfillment of performance obligations. The change in contract liabilities of $5.0 million from March 31, 2017 to December 31, 2017 is primarily due to the increase of deferrals relating to the sale of new systems.

System transactions have payment terms that are 90% due upon shipment of the tool and 10% due upon installation. Aftermarket transaction payment terms are such that payment is due either within 30 or 60 days of service provided or delivery of parts.

As of March 31, 2018, the Company had deferred revenue of $18.5 million. This represents the portion of the transaction price for contracts with customers allocated to the performance obligations that remain unsatisfied or partially unsatisfied. Short-term deferred revenue of $15.5 million represents performance obligations that will be satisfied within the next 12 months. This amount relates primarily to installation and non-standard warranty performance obligations for system sales. Long-term deferred revenue of $3.0 million relates primarily to unsatisfied extended warranty performance obligations that expected to be provided within the next 24 months.

Computation of Net Earnings per Share

3 Months Ended

Mar. 31, 2018

Computation of Net Earnings per Share

Computation of Net Earnings per Share

Note 4. Computation of Net Earnings per Share

Basic earnings per share is computed by dividing income available to common stockholders (the numerator) by the weighted‑average number of common shares outstanding (the denominator) for the period. The computation of diluted earnings per share is similar to basic earnings per share, except that the denominator is increased by the number of additional common shares that would have been outstanding if the potentially dilutive common shares issuable for stock options and restricted stock units had been issued, calculated using the treasury stock method.

The components of net earnings per share are as follows:


	Three months ended March 31,
	2018		2017
	(in thousands, except per share amounts)
Net income available to common stockholders	$	13,915	$	9,506
Weighted average common shares outstanding used in computing basic income per share		32,094		29,772
Incremental options and RSUs		2,029		2,483
Weighted average common shares used in computing diluted net income per share		34,123		32,255
Net income per share
Basic	$	0.43	$	0.32
Diluted	$	0.41	$	0.29

Diluted weighted average common shares outstanding does not include options and restricted stock units outstanding to purchase ten thousand and one hundred thousand common equivalent shares for the three month periods ended March 31, 2018 and 2017, respectively, as their effect would have been anti-dilutive.

Accumulated Other Comprehensive Income

3 Months Ended

Mar. 31, 2018

Accumulated Other Comprehensive Income

Accumulated Other Comprehensive Income (Loss)

Note 5. Accumulated Other Comprehensive Income

The following table presents the changes in accumulated other comprehensive income, net of tax, by component, for the three months ended March 31, 2018:


	Foreign		Defined benefit
	currency		pension plan		Total
	(in thousands)
Balance at December 31, 2017	$	2,756	$	(580)	$	2,176
Other comprehensive income and pension reclassification		1,021		30		1,051
Balance at March 31, 2018	$	3,777	$	(550)	$	3,227

Cash, cash equivalents and restricted cash

3 Months Ended

Mar. 31, 2018

Cash, cash equivalents and restricted cash

Cash, cash equivalents and restricted cash

Note 6. Cash, cash equivalents and restricted cash

The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the statement of financial position that sum to the total of the amounts shown in the statement of cash flows.


	March 31,
	2018			2017
	(in thousands)
Cash and cash equivalents	$	140,957	$	69,429
Short-term and long-term restricted cash		7,514		6,792
Total cash, cash equivalents and restricted cash	$	148,471	$	76,221

The restricted cash balance of $7.5 million as of March 31, 2018 which relates to (i) $5.9 million letter of credit associated with a security deposit for the lease of our corporate headquarters in Beverly, Massachusetts, (ii) $0.8 million letter of credit relating to workers’ compensation insurance, (iii) $0.7 million bank guarantee on a customer prepayment and (iv) $0.1 million deposit relating to customs activity. The restricted cash balance of $6.8 million as of March 31, 2017 includes the same items except for the bank guarantee.

Inventories, net

3 Months Ended

Mar. 31, 2018

Inventories, net

Inventories, net

Note 7. Inventories, net

The components of inventories are as follows:


	March 31,		December 31,
	2018		2017
	(in thousands)
Raw materials	$	88,009	$	82,313
Work in process		33,696		31,651
Finished goods (completed systems)		13,300		6,580
Inventories, net	$	135,005	$	120,544

When recorded, inventory reserves reduce the carrying value of inventories to their net realizable value. The Company establishes inventory reserves when conditions exist that indicate inventory may be in excess of anticipated demand or is obsolete based upon assumptions about future demand for the Company’s products or market conditions. The Company regularly evaluates the ability to realize the value of inventories based on a combination of factors including the following: forecasted sales or usage, estimated product end of life dates, estimated current and future market value and new product introductions. Purchasing and usage alternatives are also explored to mitigate inventory exposure.

Product Warranty

3 Months Ended

Mar. 31, 2018

Product Warranty

Product Warranty

Note 8. Product Warranty

The Company generally offers a one year warranty for all of its systems, the terms and conditions of which vary depending upon the product sold. For all systems sold, the Company accrues a liability for the estimated cost of standard warranty at the time of system shipment and defers the portion of systems revenue attributable to the fair value of non-standard warranty. Costs for non-standard warranty are expensed as incurred. Factors that affect the Company’s warranty liability include the number of installed units, historical and anticipated product failure rates, material usage and service labor costs. The Company periodically assesses the adequacy of its recorded liability and adjusts the amount as necessary.

The changes in the Company’s standard product warranty liability are as follows:


	Three months ended
	March 31,
	2018		2017
	(in thousands)
Balance at January 1 (beginning of year)	$	4,502	$	2,666
Warranties issued during the period		1,540		1,166
Settlements made during the period		(1,334)		(454)
Changes in estimate of liability for pre-existing warranties during the period		260		(254)
Balance at March 31 (end of period)	$	4,968	$	3,124

Amount classified as current	$	4,583	$	2,748
Amount classified as long-term		385		376
Total warranty liability	$	4,968	$	3,124

Fair Value Measurements

3 Months Ended

Mar. 31, 2018

Fair Value Measurements

Fair Value Measurements

Note 9. Fair Value Measurements

Certain assets on the Company’s balance sheets are reported at their fair value. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date.

(a) Fair Value Hierarchy

The accounting guidance for fair value measurement requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The standard establishes a fair value hierarchy based on the level of independent, objective evidence surrounding the inputs used to measure fair value. A financial instrument’s categorization within the fair value hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The fair value hierarchy is as follows:

Level 1 - applies to assets or liabilities for which there are quoted prices in active markets for identical assets or liabilities.

Level 2 - applies to assets or liabilities for which there are inputs other than quoted prices that are observable for the asset or liability, such as quoted prices for similar assets or liabilities in active markets; quoted prices for identical assets or liabilities in markets with insufficient volume or infrequent transactions (less active markets); or model-derived valuations in which significant inputs are observable or can be derived principally from, or corroborated by, observable market data.

Level 3 - applies to assets or liabilities for which there are unobservable inputs to the valuation methodology that are significant to the measurement of the fair value of the assets or liabilities.

(b) Fair Value Measurements

The Company’s money market funds and short-term investments are included in cash and cash equivalents in the consolidated balance sheets and are considered a level 1 investment as they are valued at quoted market prices in active markets.

The following table sets forth the Company’s assets by level within the fair value hierarchy:


	March 31, 2018
	Fair Value Measurements
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets
Cash equivalents:
Money market funds, U.S. Government Securities and Agency Investments	$	124,987	$	—	$	—	$	124,987


	December 31, 2017
	Fair Value Measurements
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets
Cash equivalents:
Money market funds, U.S. Government Securities and Agency Investments	$	116,433	$	—	$	—	$	116,433

The carrying amounts reflected in the consolidated balance sheets for accounts receivable, prepaid expenses and other current assets and non-current assets, restricted cash, accounts payable and accrued expenses approximate fair value due to their short-term maturities.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Financing Arrangements	3 Months Ended
Financing Arrangements	Mar. 31, 2018
Financing Arrangements
Financing Arrangements	Note 10. Financing Arrangements Sale Leaseback Obligation On January 30, 2015, the Company sold its corporate headquarters facility in Beverly Massachusetts for $48.9 million. As part of the sale, the Company also entered into a 22-year lease agreement. The sale leaseback is accounted for as a financing arrangement for financial reporting and, as such, the Company has recorded a financing obligation of $47.7 million as of March 31, 2018. The associated lease payments are deemed to include both an interest component and payment of principal, with the underlying liability being extinguished at the end of the original lease term. The Company posted a security deposit of $5.9 million in the form of an irrevocable letter of credit at the time of the closing. This letter of credit is cash collateralized and the associated cash posted as collateral is included in long-term restricted cash.

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2018
Income Taxes
Income Taxes	Note 11. Income Taxes During the three months ended March 31, 2018 and 2017, we recorded an income tax provision of $3.6 million and $11 thousand, respectively. The change in the income tax provision for the current quarter compared to the prior year was primarily due to the release of a significant portion of our valuation allowance in the fourth quarter of 2017. Prior to the release of the valuation allowance, the Company reported in its consolidated statements of operations only the amount of taxes actually payable. Subsequent to the release of the valuation allowance, tax expense also reflects the tax liability that would be payable without consideration of the usage of any net operating loss carryforwards. We have significant net operating loss carryforwards in the United States and certain European jurisdictions, and, as a result, we do not currently pay significant income taxes in those jurisdictions. At December 31, 2017, the Company had $90.3 million of deferred tax assets worldwide relating to net operating loss carryforwards, tax credit carryforwards and other temporary differences, which are available to reduce income tax liabilities in future years. On December 22, 2017, the Tax Cuts and Jobs Act ("TCJA") was enacted into law, which significantly changed existing U.S. tax law and includes numerous provisions that affect our business, such as reducing the U.S. federal statutory tax rate and adopting a territorial tax system. The TCJA reduces the U.S. federal statutory tax rate from 35% to 21%, effective January 1, 2018. The TCJA also includes a provision to tax global intangible low-taxed income ("GILTI") of foreign subsidiaries and a base erosion anti-abuse tax ("BEAT") measure that taxes certain payments between a U.S. corporation and its subsidiaries. The Company considered the available guidance and has incorporated the relevant provisions of GILTI into the income tax provision and concluded that the provisions of BEAT do not apply to the Company at this time. In accordance with Staff Accounting Bulletin (“SAB”) 118, the Company disclosed in its 2017 Annual Report on Form 10-K that it is able to determine a reasonable estimate for certain effects of tax reform and has recorded that estimate as a provisional amount. The Company intends to use the one-year measurement period to update the provisional amount recorded as it finalizes its analysis relating to certain matters, such as developing interpretations of provisions to the TCJA, changes to certain estimates and amounts related to the Earning and Profits of certain subsidiaries and the filing of tax returns. Also, Treasury regulations, administrative interpretations, or court decisions interpreting the TCJA may require further adjustments and changes to the provisional amounts. As of the first quarter 2018, the Company has not made any changes to its estimate for the transition tax liability.

Concentration of Risk	3 Months Ended
Concentration of Risk	Mar. 31, 2018
Concentration of Risk
Concentration of Risk	Note 12. Concentration of Risk For the three months ended March 31, 2018, two customers accounted for 25.9% and 15.4% of total revenue, respectively. For the three months ended March 31, 2017, four customers accounted for 19.2%, 16.6%, 16.4% and 16.3% of total revenue, respectively. At March 31, 2018, three customers accounted for 18.1%, 17.3% and 11.1% of accounts receivable, respectively. At December 31, 2017, three customers accounted for 19.8%, 11.8% and 10.6% of accounts receivable, respectively.

Contingencies	3 Months Ended
Contingencies	Mar. 31, 2018
Commitments and Contingencies
Commitments and Contingencies	Note 13. Contingencies (a) Litigation The Company is, from time to time, a party to litigation that arises in the normal course of its business operations. The Company is not presently a party to any litigation that it believes might have a material adverse effect on its business operations. (b) Indemnifications The Company’s system sales agreements typically include provisions under which the Company agrees to take certain actions, provide certain remedies and defend its customers against third-party claims of intellectual property infringement under specified conditions and to indemnify customers against any damage and costs awarded in connection with such claims. The Company has not incurred any material costs as a result of such indemnifications and has not accrued any liabilities related to such obligations in the accompanying consolidated financial statements.

Recent Accounting Guidance

3 Months Ended

Mar. 31, 2018

Recent Accounting Guidance

Recent Accounting Guidance

Note 14. Recent Accounting Guidance

Accounting Standards or Updates Adopted

In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, “Revenue from Contracts with Customers,” which provides guidance for revenue recognition. The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In April 2016, the FASB issued ASU 2016-10, “Revenue from Contracts with Customers” (Topic 606): Identifying Performance Obligations and Licensing, which further clarifies performance obligations in a contract with a customer. In May 2016, the FASB issued ASU 2016-12, “Revenue from Contracts with Customers” (Topic 606): Narrow-Scope Improvements and Practical Expedients, which provides a more narrow interpretation of ASU No. 2014-09. In July 2017, the FASB issued ASU 2017-13, “Revenue Recognition (Topic 605), Revenue from Contracts with Customers (Topic 606), Leases (Topic 840), and Leases (Topic 842), which clarify the transition periods related to public and private business entities. These ASUs (collectively referred to as “Topic 606”) are effective for annual reporting periods beginning after December 15, 2017 and interim periods within those annual periods.

Effective January 1, 2018, we adopted FASB ASC Topic 606, Revenue from Contracts with Customers, or ASC 606. In accordance with ASC 606, we changed certain characteristics of our revenue recognition accounting policy as described below. In our adoption, ASC 606 was applied only to open contracts using the modified retrospective method, where the cumulative effect of the initial application is recognized as an adjustment to opening retained earnings at January 1, 2018. Therefore, comparative prior periods have not been adjusted and continue to be reported under FASB ASC Topic 605, Revenue Recognition, or ASC 605.

In accordance with the new revenue standard requirements, the disclosure of the impact of adoption on our consolidated statement of operations for the three months ended March 31, 2018 and consolidated balance sheet as of March 31, 2018 was as follows (in thousands):


Consolidated Statement of Operations	As Reported March 31, 2018		ASC 606 Adjustments		Pro Forma Under ASC 605
Revenue:
Product	$	116,022	$	(1,006)	$	115,016
Total revenue		122,185		(1,006)		121,179
Gross profit		47,156		(1,006)		46,150
Income from operations		18,502		(1,006)		17,496
Income before income taxes		17,473		(1,006)		16,467
Income tax provision		3,558		(232)		3,326
Net income	$	13,915	$	(774)	$	13,141
Net income per share:
Basic	$	0.43	$	(0.02)	$	0.41
Diluted	$	0.41	$	(0.02)	$	0.39

Consolidated Balance Sheet	As Reported March 31, 2018		ASC 606 Adjustments		Pro Forma Under ASC 605
Deferred income taxes	$	80,697	$	232	$	80,929
Total assets	$	505,144	$	232	$	505,376

Deferred revenue	$	18,522	$	2,606	$	21,128
Total current liabilities		77,084		2,606		79,690
Total liabilities		133,617		2,606		136,223
Accumulated deficit		(189,230)		(2,374)		(191,604)
Total stockholders' equity		371,527		(2,374)		369,153
Total liabilities and stockholders' equity	$	505,144	$	232	$	505,376

The impact of the adoption of ASC 606 on consolidated statements of comprehensive income and cash flows for the three months ended March 31, 2018 was not material.

Upon adoption of ASC 606, we changed our accounting policy for the installation performance obligation included in all system sales. Previously under ASC 605, the Company deferred revenue for the greater of the fair value of the installation or the portion of contract consideration for which collection was contingent upon installation completion (the “retention”). The concept of contingent consideration is no longer relevant under ASC 606 and therefore we will only defer the portion of the transaction price allocated to the installation performance obligation. As a result of this change, we recorded a cumulative effect adjustment to increase retained earnings and decrease deferred revenue on January 1, 2018 by $1.6 million. Upon the adoption, all new contracts will be accounted for under ASC 606. Disclosures related to the nature, amount and timing of revenue and cash flows arising from contracts with customers are included in Note 3.

In August 2016, the FASB issued ASU No. 2016-15 “Classification of Certain Cash Receipts and Cash Payments.” The ASU is intended to add or clarify guidance on the classification relating to specific cash flow receipts and payments in the statement of cash flows and to eliminate the diversity in practice related to such classifications. The guidance in ASU 2016-15 is required for annual reporting periods beginning after December 15, 2017, and is to be applied retrospectively for each period presented. Adoption of ASU 2016-15 had no material effect on our consolidated financial statements and disclosures.

In March 2017, the FASB issued ASU No. 2017-07 “Compensation – Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost.” The ASU is intended to improve the presentation of net periodic pension cost and net periodic postretirement benefit cost. The amendment applies to all entities offering a defined benefit pension plan, other postretirement benefit plans, or other types of benefits accounted for under Topic 715. The amendments in the ASU require an employer to report the service cost component in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of net benefit cost are required to be presented in the income statement separately from the service cost component and outside a subtotal of income from operations. The amendments in this ASU are effective for public business entities for annual periods beginning after December 15, 2017, including interim periods within the annual period. The amendments in this ASU should be applied retrospectively for the presentation of the service cost component and the other components of net periodic pension cost and net periodic postretirement benefit cost in the income statement and prospectively, on and after the effective date, for the capitalization of the service cost component of net periodic pension cost and net periodic postretirement benefit in assets. Adoption of ASU 2017-07 had no material effect on the consolidated financial statements and disclosures.

Accounting Standards or Updates Not Yet Effective

In February 2016, the FASB issued ASU No. 2016-02 “Leases.” The ASU requires lessees to recognize the rights and obligations created by most leases as assets and liabilities on their balance sheet and continue to recognize expenses on their income statement over the lease term. It will also require disclosures designed to give financial statement users information on the amount, timing, and uncertainty of cash flows arising from leases. The guidance is effective for annual reporting periods beginning after December 15, 2018, and interim periods within those years. Early adoption is permitted for all entities. We are currently evaluating the impact of ASU 2016-02 on the consolidated financial statements and disclosures. The Company anticipates adopting the new standard on January 1, 2019 using the modified retrospective approach with the primary effect of adopting the new standard to be the recognition of additional assets and corresponding liabilities related to operating leases. The adoption is not expected to have a material impact on the Company’s results of operations and cash flows.

Revenue (Tables)

3 Months Ended

Mar. 31, 2018

Revenue

Schedule of revenue by discipline


	Three months ended
	March 31,
	2018*		2017
	(in thousands)
Systems	$	85,475	$	55,249
Aftermarket		36,710		31,644
	$	122,185	$	86,893

Schedule of revenue by geographic markets


	Three months ended
	March 31,
	2018*		2017
	(in thousands)
North America	$	10,523	$	6,997
Asia		97,689		63,245
Europe		13,973		16,651
	$	122,185	$	86,893

Schedule of contract assets and contract liabilities


	March 31,		December 31,		March 31,
	2018		2017		2017
	(in thousands)
Contract assets	$	—	$	—	$	—

Contract liabilities	$	18,522	$	18,145	$	13,121

Revenue recognized in the period from:
Amounts included in contract liability at the beginning of the period	$	6,342	$	9,105	$	5,277
Performance obligations satisfied in previous periods	$	—	$	—	$	—

Computation of Net Earnings per Share (Tables)

3 Months Ended

Mar. 31, 2018

Computation of Net Earnings per Share

Schedule of components of net income per share


	Three months ended March 31,
	2018		2017
	(in thousands, except per share amounts)
Net income available to common stockholders	$	13,915	$	9,506
Weighted average common shares outstanding used in computing basic income per share		32,094		29,772
Incremental options and RSUs		2,029		2,483
Weighted average common shares used in computing diluted net income per share		34,123		32,255
Net income per share
Basic	$	0.43	$	0.32
Diluted	$	0.41	$	0.29

Accumulated Other Comprehensive Income (Tables)

3 Months Ended

Mar. 31, 2018

Accumulated Other Comprehensive Income

Schedule of changes in accumulated other comprehensive income, net of tax


	Foreign		Defined benefit
	currency		pension plan		Total
	(in thousands)
Balance at December 31, 2017	$	2,756	$	(580)	$	2,176
Other comprehensive income and pension reclassification		1,021		30		1,051
Balance at March 31, 2018	$	3,777	$	(550)	$	3,227

Cash, cash equivalents and restricted cash (Tables)

3 Months Ended

Mar. 31, 2018

Cash, cash equivalents and restricted cash

Schedule of reconciliation of cash, cash equivalents and restricted cash


	March 31,
	2018			2017
	(in thousands)
Cash and cash equivalents	$	140,957	$	69,429
Short-term and long-term restricted cash		7,514		6,792
Total cash, cash equivalents and restricted cash	$	148,471	$	76,221

Inventories, net (Tables)

3 Months Ended

Mar. 31, 2018

Inventories, net

Schedule of components of inventories


	March 31,		December 31,
	2018		2017
	(in thousands)
Raw materials	$	88,009	$	82,313
Work in process		33,696		31,651
Finished goods (completed systems)		13,300		6,580
Inventories, net	$	135,005	$	120,544

Product Warranty (Tables)

3 Months Ended

Mar. 31, 2018

Product Warranty

Schedule of product warranty liability


	Three months ended
	March 31,
	2018		2017
	(in thousands)
Balance at January 1 (beginning of year)	$	4,502	$	2,666
Warranties issued during the period		1,540		1,166
Settlements made during the period		(1,334)		(454)
Changes in estimate of liability for pre-existing warranties during the period		260		(254)
Balance at March 31 (end of period)	$	4,968	$	3,124

Amount classified as current	$	4,583	$	2,748
Amount classified as long-term		385		376
Total warranty liability	$	4,968	$	3,124

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2018

Fair Value Measurements

Schedule of Company's assets and liabilities by level within the fair value hierarchy


	March 31, 2018
	Fair Value Measurements
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets
Cash equivalents:
Money market funds, U.S. Government Securities and Agency Investments	$	124,987	$	—	$	—	$	124,987


	December 31, 2017
	Fair Value Measurements
	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets
Cash equivalents:
Money market funds, U.S. Government Securities and Agency Investments	$	116,433	$	—	$	—	$	116,433

Recent Accounting Guidance (Tables)

3 Months Ended

Mar. 31, 2018

ASU 2014-09

New Accounting Pronouncements Or Change In Accounting Principle [LineItems]

Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block]


Consolidated Statement of Operations	As Reported March 31, 2018		ASC 606 Adjustments		Pro Forma Under ASC 605
Revenue:
Product	$	116,022	$	(1,006)	$	115,016
Total revenue		122,185		(1,006)		121,179
Gross profit		47,156		(1,006)		46,150
Income from operations		18,502		(1,006)		17,496
Income before income taxes		17,473		(1,006)		16,467
Income tax provision		3,558		(232)		3,326
Net income	$	13,915	$	(774)	$	13,141
Net income per share:
Basic	$	0.43	$	(0.02)	$	0.41
Diluted	$	0.41	$	(0.02)	$	0.39

Consolidated Balance Sheet	As Reported March 31, 2018		ASC 606 Adjustments		Pro Forma Under ASC 605
Deferred income taxes	$	80,697	$	232	$	80,929
Total assets	$	505,144	$	232	$	505,376

Deferred revenue	$	18,522	$	2,606	$	21,128
Total current liabilities		77,084		2,606		79,690
Total liabilities		133,617		2,606		136,223
Accumulated deficit		(189,230)		(2,374)		(191,604)
Total stockholders' equity		371,527		(2,374)		369,153
Total liabilities and stockholders' equity	$	505,144	$	232	$	505,376

Stock-Based Compensation - (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stock-based compensation
Stock-based compensation expense	$ 1,100
Proceeds from exercise of stock options	$ 446	$ 2,531
Common Stock
Stock-based compensation
Exercise of stock options (in shares)	100,000	500,000
Proceeds from exercise of stock options	$ 400	$ 2,500
2000 Stock Plan
Stock-based compensation
Number of shares of common stock available for future grant	0

Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
Revenue (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Product warranty period	1 year
Change in contract liabilities		$ 5,000
Deferred revenue	$ 15,507	16,181
Long-term deferred revenue	3,015	$ 1,964
ASC 606 Adjustments
Disaggregation of Revenue [Line Items]
Increase in revenue	$ (1,006)
ASC 606 Adjustments \| Maximum
Disaggregation of Revenue [Line Items]
Unsatisfied extended warranty performance obligations, period	24 months
Systems
Disaggregation of Revenue [Line Items]
Payment upon shipment of tool, as a percent	90.00%
Payment upon installation, as a percent	10.00%
Systems \| Minimum
Disaggregation of Revenue [Line Items]
Payment upon delivery of parts, period	30 days
Systems \| Maximum
Disaggregation of Revenue [Line Items]
Payment upon delivery of parts, period	60 days
Systems \| ASC 606 Adjustments
Disaggregation of Revenue [Line Items]
Increase in revenue	$ 1,000

Revenue - Revenue by discipline & geographical areas (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 122,185
North America
Disaggregation of Revenue [Line Items]
Revenue	10,523
Asia
Disaggregation of Revenue [Line Items]
Revenue	97,689
Europe
Disaggregation of Revenue [Line Items]
Revenue	13,973
Systems
Disaggregation of Revenue [Line Items]
Revenue	85,475
Aftermarket
Disaggregation of Revenue [Line Items]
Revenue	36,710
Before Topic 606
Disaggregation of Revenue [Line Items]
Revenue	121,179	$ 86,893
Before Topic 606 \| North America
Disaggregation of Revenue [Line Items]
Revenue		6,997
Before Topic 606 \| Asia
Disaggregation of Revenue [Line Items]
Revenue		63,245
Before Topic 606 \| Europe
Disaggregation of Revenue [Line Items]
Revenue		16,651
Before Topic 606 \| Systems
Disaggregation of Revenue [Line Items]
Revenue		55,249
Before Topic 606 \| Aftermarket
Disaggregation of Revenue [Line Items]
Revenue		$ 31,644
ASC 606 Adjustments \| North America
Disaggregation of Revenue [Line Items]
Revenue	300
ASC 606 Adjustments \| Asia
Disaggregation of Revenue [Line Items]
Revenue	1,500
ASC 606 Adjustments \| Europe
Disaggregation of Revenue [Line Items]
Revenue	$ 200

Revenue - Contract assets and liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Revenue
Contract liabilities	$ 18,522	$ 13,121	$ 18,145
Revenue recognized in the period from:
Amounts included in contract liability at the beginning of the period	$ 6,342	$ 5,277	$ 9,105

Computation of Net Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Computation of Net Earnings per Share
Net income available to common stockholders	$ 13,915	$ 9,506
Weighted average common shares outstanding used in computing basic income per share	32,094	29,772
Incremental options and RSUs	2,029	2,483
Weighted average common shares used in computing diluted net income per share	34,123	32,255
Net income per share
Basic	$ 0.43	$ 0.32
Diluted	$ 0.41	$ 0.29
Weighted average number diluted shares outstanding adjustment	10	100

Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Changes in accumulated other comprehensive income, net of tax
Balance at December 31, 2017	$ 2,176
Other comprehensive income and pension reclassification	1,051	$ 1,943
Balance at March 31, 2018	3,227
Foreign currency
Changes in accumulated other comprehensive income, net of tax
Balance at December 31, 2017	2,756
Other comprehensive income and pension reclassification	1,021
Balance at March 31, 2018	3,777
Defined benefit pension plan
Changes in accumulated other comprehensive income, net of tax
Balance at December 31, 2017	(580)
Other comprehensive income and pension reclassification	30
Balance at March 31, 2018	$ (550)

Cash, cash equivalents and restricted cash (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash and cash equivalents	$ 140,957	$ 133,407	$ 69,429
Short-term and long-term restricted cash	7,514		6,792
Total cash, cash equivalents and long-term restricted cash	148,471		76,221	$ 140,880	$ 77,655
Letter of credit related to workers' compensation insurance	800
Letter of credit associated with a bank guarantee	700
Deposit related to customs activity	100
Revolving credit facility
Restricted cash which relates to support of outstanding letters of credit	7,500		$ 6,800
Revolving credit facility \| Beverly Property Owner LLC
Letter of credit associated with security deposit for leaseback transaction	$ 5,900

Inventories, net (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Inventories, net
Raw materials	$ 88,009	$ 82,313
Work in process	33,696	31,651
Finished goods (completed systems)	13,300	6,580
Inventories, net	$ 135,005	$ 120,544

Product Warranty (Details) - USD ($) $ in Thousands	3 Months Ended
Product Warranty (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Product Warranty
Product warranty period	1 year
Changes in standard product warranty liability
Balance at January 1 (beginning of year)	$ 4,502	$ 2,666
Warranties issued during the period	1,540	1,166
Settlements made during the period	(1,334)	(454)
Changes in estimate of liability for pre-existing warranties during the period	260	(254)
Balance at March 31 (end of period)	4,968	3,124
Product warranty classification
Amount classified as current			$ 4,583	$ 4,112	$ 2,748
Amount classified as long-term			385		376
Total warranty liability	$ 4,502	$ 2,666	$ 4,968	$ 4,502	$ 3,124

Fair Value Measurements (Details) - Recurring - Money market funds, US Government Securities and Agency Investments - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Total
Fair Value Measurements
Money market funds, US Government Securities and Agency Investments	$ 124,987	$ 116,433
Level 1
Fair Value Measurements
Money market funds, US Government Securities and Agency Investments	$ 124,987	$ 116,433

Financing Arrangements (Details) - USD ($) $ in Thousands	Jan. 30, 2015	Mar. 31, 2018	Dec. 31, 2017
Financing Arrangements
Sale leaseback obligation		$ 47,724	$ 47,714
Beverly Property Owner LLC \| Sale leaseback obligation \| Buildings
Financing Arrangements
Purchase price	$ 48,900
Lease term	22 years
Sale leaseback obligation		47,700
Security deposit		$ 5,900

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Income Taxes
Income tax provision	$ 3,558	$ 11
Deferred tax assets valuation allowance			$ 90,300
Federal statutory tax rate	21.00%		35.00%

Concentration of Risk (Details) - customer	3 Months Ended		12 Months Ended
Concentration of Risk (Details) - customer	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Revenue \| Customer concentration risk
Concentration of risk
Number of customers	2	4
Revenue \| Customer concentration risk \| First customer
Concentration of risk
Percentage of concentration risk	25.90%	19.20%
Revenue \| Customer concentration risk \| Second customer
Concentration of risk
Percentage of concentration risk	15.40%	16.60%
Revenue \| Customer concentration risk \| Third customer
Concentration of risk
Percentage of concentration risk		16.40%
Revenue \| Customer concentration risk \| Fourth customer
Concentration of risk
Percentage of concentration risk		16.30%
Consolidated accounts receivable \| Credit concentration risk
Concentration of risk
Number of customers	3		3
Consolidated accounts receivable \| Credit concentration risk \| First customer
Concentration of risk
Percentage of concentration risk	18.10%		19.80%
Consolidated accounts receivable \| Credit concentration risk \| Second customer
Concentration of risk
Percentage of concentration risk	17.30%		11.80%
Consolidated accounts receivable \| Credit concentration risk \| Third customer
Concentration of risk
Percentage of concentration risk	11.10%		10.60%

Recent Accounting Guidance (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017
Revenue:
Revenue	$ 122,185
Gross profit	47,156	$ 34,714
Income from operations	18,502	10,713
Income before income taxes	17,473	9,517
Income tax provision	3,558	11
Net income	$ 13,915	$ 9,506
Net income per share:
Basic (in dollars per share)	$ 0.43	$ 0.32
Diluted (in dollars per share)	$ 0.41	$ 0.29
Consolidated Balance Sheet
Deferred income taxes	$ 80,697			$ 83,148
Total assets	505,144			488,218
Deferred revenue	18,522	$ 13,121		18,145
Total current liabilities	77,084			79,287
Total liabilities	133,617			134,608
Retained Earnings (Accumulated Deficit)	(189,230)			(204,745)
Total stockholders' equity	371,527			353,610
Total liabilities and stockholders' equity	505,144			488,218
Cumulative adjustment in deferred revenue				$ (5,000)
Product
Revenue:
Revenue	116,022
ASC 606 Adjustments
Revenue:
Revenue	(1,006)
Gross profit	(1,006)
Income from operations	(1,006)
Income before income taxes	(1,006)
Income tax provision	(232)
Net income	$ (774)
Net income per share:
Basic (in dollars per share)	$ (0.02)
Diluted (in dollars per share)	$ (0.02)
Consolidated Balance Sheet
Deferred income taxes	$ 232
Total assets	232
Deferred revenue	2,606
Total current liabilities	2,606
Total liabilities	2,606
Retained Earnings (Accumulated Deficit)	(2,374)
Total stockholders' equity	(2,374)
Total liabilities and stockholders' equity	232
ASC 606 Adjustments \| Product
Revenue:
Revenue	(1,006)
ASC 606 Adjustments \| ASU 2014-09
Consolidated Balance Sheet
Cumulative adjustment increase in retained earnings			$ 1,600
Cumulative adjustment in deferred revenue			$ 1,600
Before Topic 606
Revenue:
Revenue	121,179	$ 86,893
Gross profit	46,150
Income from operations	17,496
Income before income taxes	16,467
Income tax provision	3,326
Net income	$ 13,141
Net income per share:
Basic (in dollars per share)	$ 0.41
Diluted (in dollars per share)	$ 0.39
Consolidated Balance Sheet
Deferred income taxes	$ 80,929
Total assets	505,376
Deferred revenue	21,128
Total current liabilities	79,690
Total liabilities	136,223
Retained Earnings (Accumulated Deficit)	(191,604)
Total stockholders' equity	369,153
Total liabilities and stockholders' equity	505,376
Before Topic 606 \| Product
Revenue:
Revenue	$ 115,016