Neophotonics (NPTN) 10-Q 5 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 31, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Trading Symbol	NPTN
Entity Registrant Name	NEOPHOTONICS CORP
Entity Central Index Key	1,227,025
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		46,049,277

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 52,099	$ 78,906
Short-term investments	7,441	12,311
Restricted cash	5,195	2,658
Accounts receivable, net of allowance for doubtful accounts	66,620	67,229
Inventories	57,124	67,301
Assets held for sale	3,192	0
Prepaid expenses and other current assets	28,659	36,235
Total current assets	220,330	264,640
Property, plant and equipment, net	104,965	127,565
Purchased intangible assets, net	3,320	4,294
Goodwill	1,115	1,115
Other long-term assets	3,080	5,339
Total assets	332,810	402,953
Current liabilities:
Accounts payable	54,603	69,017
Notes payable and short-term borrowing	3,634	35,607
Current portion of long-term debt	2,798	6,005
Accrued and other current liabilities	46,857	43,242
Total current liabilities	107,892	153,871
Long-term debt, net of current portion	50,356	40,556
Other noncurrent liabilities	13,388	14,075
Total liabilities	171,636	208,502
Commitments and contingencies (Note 11)
Stockholders’ equity:
Preferred stock, $0.0025 par value, 10,000 shares authorized, no shares issued or outstanding	0	0
Common stock, $0.0025 par value, 100,000 shares authorized; At September 30, 2018, 45,840 shares issued and outstanding; as of December 31, 2017, 44,219 shares issued and outstanding	115	111
Additional paid-in capital	559,371	545,953
Accumulated other comprehensive income (loss)	(7,569)	398
Accumulated deficit	(390,743)	(352,011)
Total stockholders’ equity	161,174	194,451
Total liabilities and stockholders’ equity	$ 332,810	$ 402,953

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.0025	$ 0.0025
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0025	$ 0.0025
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	45,840,000	44,219,000
Common stock, shares outstanding (in shares)	45,840,000	44,219,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Revenue	$ 81,748	$ 71,121	$ 231,436	$ 216,023
Cost of goods sold	62,815	60,608	187,849	170,230
Gross profit	18,933	10,513	43,587	45,793
Operating expenses:
Research and development	13,177	14,662	40,308	44,412
Sales and marketing	4,351	4,071	12,366	12,913
General and administrative	8,592	7,637	23,509	26,792
Amortization of purchased intangible assets	118	119	357	355
Asset sale related costs	251	78	344	229
Restructuring charges	1,133	2,829	1,786	3,550
Gain on asset sale	0	0	0	(2,000)
Total operating expenses	27,622	29,396	78,670	86,251
Loss from operations	(8,689)	(18,883)	(35,083)	(40,458)
Interest income	85	37	300	141
Interest expense	(540)	(495)	(2,007)	(743)
Other income (expense), net	1,310	(41)	1,891	197
Total interest and other income (expense), net	855	(499)	184	(405)
Loss before income taxes	(7,834)	(19,382)	(34,899)	(40,863)
Income tax (provision) benefit	(291)	1,195	(2,009)	1,813
Net loss	$ (8,125)	$ (18,187)	$ (36,908)	$ (39,050)
Basic net loss per share (USD per share)	$ (0.18)	$ (0.42)	$ (0.82)	$ (0.90)
Diluted net loss per share (USD per share)	$ (0.18)	$ (0.42)	$ (0.82)	$ (0.90)
Weighted average shares used to compute basic net loss per share (in shares)	45,476	43,790	44,804	43,212
Weighted average shares used to compute diluted net loss per share (in shares)	45,476	43,790	44,804	43,212

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (8,125)	$ (18,187)	$ (36,908)	$ (39,050)
Other comprehensive income (loss):
Foreign currency translation adjustments, net of zero tax	(5,588)	2,177	(7,968)	6,090
Unrealized gains on available-for-sale securities, net of zero tax	0	1	1	17
Total other comprehensive income (loss)	(5,588)	2,178	(7,967)	6,107
Comprehensive loss	$ (13,713)	$ (16,009)	$ (44,875)	$ (32,943)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities
Net loss	$ (36,908)	$ (39,050)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	23,551	20,630
Stock-based compensation expense	10,527	5,692
Deferred taxes	(42)	673
Others	327	158
Loss (gain) on sale of assets and other write-offs	304	(1,623)
Loss (gain) on foreign currency hedges	2,220	(1,501)
Allowance for doubtful accounts	(144)	76
Write-down of inventories	3,200	7,083
Asset impairment charge	0	275
Foreign currency remeasurement	(4,192)	1,576
Change in assets and liabilities, net of effects of asset sale:
Accounts receivable	519	13,755
Inventories	5,482	(36,466)
Prepaid expenses and other assets	5,957	(12,002)
Accounts payable	(4,958)	(9,424)
Accrued and other liabilities	3,154	8,937
Net cash provided by (used in) operating activities	8,997	(41,211)
Cash flows from investing activities
Purchase of property, plant and equipment	(14,377)	(41,461)
Proceeds from sale of property, plant and equipment and other assets	32	21,806
Purchase of marketable securities	(880)	(52,031)
Proceeds from sale of marketable securities	5,000	52,272
Proceeds from maturity of marketable securities	750	6,458
Settlement of foreign currency hedges	(1,776)	1,553
Net cash used in investing activities	(11,251)	(11,403)
Cash flows from financing activities
Proceeds from exercise of stock options and issuance of stock under ESPP	3,801	3,568
Tax withholding on restricted stock units	(747)	(973)
Payments for public stock offering	0	(117)
Proceeds from bank loans, net of debt issuance costs	29,358	96,039
Repayment of bank loans	(57,323)	(68,270)
Proceeds from issuance of notes payable	4,795	5,842
Repayment of notes payable	(2,568)	(9,789)
Proceeds from government grants	1,228	0
Net cash (used in) provided by financing activities	(21,456)	26,300
Effect of exchange rates on cash, cash equivalents and restricted cash	(560)	1,174
Net decrease in cash, cash equivalents and restricted cash	(24,270)	(25,140)
Cash, cash equivalents and restricted cash at the beginning of the period	81,564	86,585
Cash, cash equivalents and restricted cash at the end of the period	57,294	61,445
Supplemental disclosure of non-cash investing and financing activities:
Decrease in unpaid property, plant and equipment	8,916	6,430
Asset retirement obligations	$ 0	$ 2,146

Basis of presentation and signi

Basis of presentation and significant accounting policies	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation and significant accounting policies	Basis of presentation and significant accounting policies Basis of Presentation and Consolidation The condensed consolidated financial statements of NeoPhotonics Corporation (“NeoPhotonics” or the “Company”) as of September 30, 2018 and for the three and nine months ended September 30, 2018 and 2017 , have been prepared in accordance with the instructions on Form 10-Q pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). In accordance with those rules and regulations, the Company has omitted certain information and notes normally provided in the Company’s annual consolidated financial statements. In the opinion of management, the condensed consolidated financial statements contain all adjustments, consisting only of normal recurring items, except as otherwise noted, necessary for the fair presentation of the Company’s financial position and results of operations for the interim periods. The year-end condensed consolidated balance sheet data was derived from audited financial statements, but does not include all disclosures required by U.S. generally accepted accounting principles (“U.S. GAAP”). These condensed consolidated financial statements should be read in conjunction with the Consolidated Financial Statements and Notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2017 . The results of operations for the three and nine months ended September 30, 2018 are not necessarily indicative of the results expected for the entire fiscal year. All intercompany accounts and transactions have been eliminated. Going Concern Accounting Standards Update (“ASU”) No. 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern , requires an entity to disclose information about its potential inability to continue as a going concern when conditions and events indicate that it is probable that the entity may be unable to meet its obligations as they become due within one year. Management has assessed the Company’s ability to continue as a going concern within one year of the filing date of this Quarterly Report on Form 10-Q with the SEC in November 2018. The accompanying unaudited condensed financial statements have been prepared assuming that the Company will continue as a going concern, which contemplates the realization of assets and satisfaction of liabilities in the normal course of business. As of September 30, 2018 , the Company’s working capital was $112.4 million , including available cash, cash equivalents, short-term investments and restricted cash of approximately $64.7 million . In the first nine months of 2018, the Company had operating losses of $35.1 million and cash from operations of $9.0 million . It had an accumulated deficit of approximately $390.7 million as of September 30, 2018 . Through 2017 and the early part of 2018, the Company's operating results and cash flows were negatively affected by demand that was lower than customer estimates that were used to put capacity in place over the last two years. In the three months ended June 30, 2018, demand continued to be strong, primarily due to volume growth in the Americas and the result of increased domestic deployments in China plus exports for international deployments. In the three months ended September 30, 2018, demand was in line with the increased demand experienced during the three months ended June 30, 2018. To adjust to the demand that was less than estimates used for capacity decisions, the Company implemented restructuring plans in May and September 2017 that included a reduction in force and consolidation of facilities, in order to reduce expenses. The Company has also reduced or delayed certain product development projects and capital expenditures, aggressively pursued collections of accounts and notes receivable and continued to closely manage production and inventory levels. In September 2017, the Company entered into a revolving line of credit agreement with Wells Fargo Bank, National Association ("Wells Fargo") which provides for borrowings under an accounts receivable based formula up to a maximum of $50.0 million . As of September 30, 2018, $35.6 million was outstanding under this line. The remaining borrowing capacity as of September 30, 2018 was $14.4 million , of which $5.0 million is required to be maintained as unused borrowing capacity. Borrowings under the Wells Fargo line are not due until June 30, 2022 as long as the borrowing base is not less than the outstanding amount (See Note 9). Additionally, the Company had $3.6 million of notes payable and $2.8 million of current portion of long-term debt as of September 30, 2018 , which it plans to pay out of its existing available cash. The Company currently believes it will have sufficient resources to fund its currently planned operations and expenditures over the next twelve months without additional financing or other actions. In addition, the Company believes there are a number of ongoing and potential actions that may further strengthen its projected cash and projected financial position. The Company operates in an industry in which it is difficult to evaluate its prospects with certainty. Future declines in China market demand or other changes to the Company’s forecasts could adversely affect the Company’s results of operations, financial position and cash flows. As a result, the Company may need to raise additional debt or equity capital to fund its operations. Any additional debt arrangements may likely require regular interest and principal payments which could adversely affect the Company’s operations. There can be no assurance that additional debt or equity capital will be available on acceptable terms, or at all. Certain Significant Risks and Uncertainties The Company operates in a dynamic industry and, accordingly, can be affected by a variety of factors. For example, any of the following areas could have a negative effect on the Company in terms of its future financial position, results of operations or cash flows: the general state of the U.S., China and world economies; the highly cyclical nature of the industries the Company serves; the loss of any of a small number of its larger customers; ability to obtain additional financing; inability to meet certain debt covenants; fundamental changes in the technology underlying the Company’s products; the hiring, training and retention of key employees; successful and timely completion of product design efforts; and new product design introductions by competitors. Concentration In the three months ended September 30, 2018 , Huawei Technologies Co. Ltd. and its affiliate HiSilicon Technologies (together with Huawei Technologies Co. Ltd., "Huawei") accounted for approximately 47% of the Company's total revenue. One other customer accounted for approximately 28% of the Company’s total revenue and the Company’s top five customers represented approximately 89% of the Company’s total revenue. In the three months ended September 30, 2017 , Huawei accounted for approximately 39% of the Company's total revenue. Two other customers accounted for approximately 14% and 11% of the Company’s total revenue and the Company’s top five customers represented approximately 79% of the Company’s total revenue. In the nine months ended September 30, 2018, Huawei accounted for approximately 47% of the Company's total revenue. One other customer accounted for approximately 25% of the Company's total revenue and the Company's top five customers represented approximately 89% of its total revenue. In the nine months ended September 30, 2017, Huawei accounted for approximately 39% of the Company's total revenue. One other customer accounted for approximately 16% of the Company's total revenue and the Company's top five customers represented approximately 76% of the Company's total revenue. As of September 30, 2018 , three customers accounted for approximately 41% , 20% and 12% of the Company’s accounts receivable. As of December 31, 2017 , three customers accounted for approximately 36% , 14% and 10% , respectively, of the Company’s accounts receivable. Use of Estimates The preparation of financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported revenue and expenses during the reporting period. Significant estimates made by management include: the useful lives of property, plant and equipment and intangible assets as well as future cash flows to be generated by those assets; fair values of identifiable assets acquired and liabilities assumed in business combinations; allowances for doubtful accounts; valuation allowances for deferred tax assets; valuation of excess and obsolete inventories; warranty reserves; litigation accrual and recognition of stock-based compensation, among others. Actual results could differ from these estimates. Accounting Standards Update Recently Adopted In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2014-9, Revenue from Contracts with Customers (“ASU 2014-9”). The standard, along with the amendments issued in 2016 and 2015, provides companies with a single model for use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific revenue guidance. The core principle of the model is to recognize revenue when control of the goods or services transfers to the customer, as opposed to recognizing revenue when the risks and rewards transfer to the customer under the existing revenue guidance. ASU 2014-9 is required to be adopted, using either of two methods: (i) retrospective to each prior reporting period presented with the option to elect certain practical expedients as defined within ASU 2014-9; or (ii) retrospective with the cumulative effect of initially applying ASU 2014-9 recognized at the date of initial application and providing certain additional disclosures. This standard, as amended, is effective for annual and interim periods beginning after December 15, 2017 and permits entities to early adopt for annual and interim reporting periods beginning after December 15, 2016. The Company adopted this standard as of January 1, 2018, using the full retrospective transition method. See Note 2 for further details. In May 2017, the FASB issued ASU No. 2017-9, Compensation—Stock Compensation (718)—Scope of Modification Accounting (ASU 2017-9”). This guidance redefines which changes to the terms and conditions of a share-based payment award require an entity to apply modification accounting for a share-based payment. ASU 2017-9 is effective for interim and annual periods after December 15, 2017 and early adoption is permitted in any interim period. The Company adopted this standard effective January 1, 2018. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. In January 2017, the FASB issued ASU 2017-1, Business Combinations (Topic 805): Clarifying the Definition of a Business (“ASU 2017-1”). This standard provides a framework in determining when a set of assets and activities is a business. ASU 2017-1 is effective for interim and annual periods beginning after December 15, 2017 on a prospective basis. The Company adopted this standard effective January 1, 2018. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (“ASC 2016-18”). This standard provides guidance on the classification and presentation of restricted cash in the statement of cash flows and must be applied retrospectively. ASU 2016-18 is effective for fiscal years beginning after December 15, 2017. The Company adopted this standard effective January 1, 2018. The reclassified restricted cash balances from investing activities to changes in cash, cash equivalents and restricted cash on the condensed consolidated statements of cash flows were not material for all periods presented. In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory (“ASU 2016-16”). This standard provides guidance on the tax accounting for the transferring and receiving entities upon transfer of an asset. ASU 2016-16 is effective for the Company’s interim and annual periods beginning after December 15, 2017 and should be applied on a modified retrospective basis. Upon adoption of this standard on January 1, 2018, the Company recorded $1.8 million to accumulated deficit balance for intra-entity transfer of an asset other than inventory in prior years. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”). This standard provides guidance on the classification of certain cash receipts and payments in the statement of cash flows. It is effective, retrospectively, for the Company’s annual and interim reporting periods beginning after December 15, 2017 or prospectively from the earliest date practicable if retrospective application is impracticable. The Company adopted this standard effective January 1, 2018, using the retrospective transition method. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. In January 2016, the FASB issued ASU 2016-1, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities (“ASU 2016-1”). ASU 2016-1 revises an entity’s accounting related to (1) the classification and measurement of investments in equity securities and (2) the presentation of certain fair value changes for financial liabilities measured at fair value. It also amends certain disclosure requirements associated with the fair value of financial instruments and is effective for the Company’s annual and interim reporting periods beginning after December 15, 2017. The Company adopted this standard effective January 1, 2018. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. In March 2017, the FASB issued ASU No. 2017-7, Compensation-Retirement Benefits (Topic 715)-Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost (“ASU 2017-7”). This guidance revises the presentation of employer-sponsored defined benefit pension and other postretirement plans for the net periodic benefit cost in the statement of operations and requires that the service cost component of net periodic benefit be presented in the same income statement line items as other employee compensation costs for services rendered during the period. The other components of the net benefit costs are required to be presented in the statement of operations separately from the service cost component and outside the subtotal of income from operations. This guidance allows only the service cost component of net periodic benefit costs to be eligible for capitalization. ASU 2017-7 is effective for interim and annual periods after December 15, 2017. The Company adopted this standard effective January 1, 2018. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. There have been no other changes in the Company’s significant accounting policies in the nine months ended September 30, 2018, as compared to the significant accounting policies described in its Annual Report on Form 10-K for the year ended December 31, 2017 . Recent Accounting Standards Update Not Yet Effective In January 2017, the FASB issued ASU 2017-4, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (“ASU 2017-4”). This standard amends the goodwill impairment test to compare the fair value of a reporting unit with its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value, up to the total amount of goodwill allocated to that reporting unit. ASU 2017-4 is effective prospectively for interim and annual periods beginning after December 15, 2019. Early adoption is permitted for interim and annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company has not determined whether it will elect early adoption and is currently evaluating the impact of the adoption of this standard on its consolidated financial statements and related disclosures. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 amends existing guidance on the impairment of financial assets and adds an impairment model that is based on expected losses rather than incurred losses and requires an entity to recognize as an allowance its estimate of expected credit losses for its financial assets. An entity will apply this guidance through a cumulative-effect adjustment to retained earnings upon adoption (a modified-retrospective approach) while a prospective transition approach is required for debt securities for which an other-than-temporary impairment had been recognized before the effective date. It is effective for the Company’s annual and interim reporting periods beginning after December 15, 2019. Early adoption is permitted. The Company is in the process of evaluating the impact of the adoption on its consolidated financial statements and related disclosure. In February 2016, the FASB issued ASU 2016-2, Leases (Topic 842) (“ASU 2016-2”). ASU 2016-2 introduces a lessee model that requires recognition of assets and liabilities arising from qualified leases on the consolidated balance sheets and consolidated statements of operations and to disclose qualitative and quantitative information about lease transactions. It is effective for interim and annual periods beginning after December 15, 2018. Early adoption is permitted. Certain optional practical expedients are allowed. The Company is in the process of evaluating the impact of the adoption on its consolidated financial statements and related disclosure.

Revenue

Revenue	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Adoption of ASC Topic 606, “Revenue from Contracts with Customers” On January 1, 2018, the Company adopted Topic 606 using the full retrospective method which required it to restate each prior reporting period presented. The adoption did not have a material impact on the Company's consolidated financial statements and as a result, no changes were made to prior reporting periods presented. Product revenue The Company develops, manufactures and sells optoelectronic products that transmit, receive, modify and switch high speed digital optical signals for communications networks. Revenue is derived primarily from the sale of hardware products. The Company sells its products worldwide, primarily to leading network equipment manufacturers. Revenue recognition Revenue is recognized upon transfer of control of promised products or services to customers in an amount that reflects the consideration the Company expects to receive in exchange for those products or services. The Company generally bears all costs, risk of loss or damage and retains title to the goods up to the point of transfer of control of promised products to customer. Revenue related to the sale of consignment inventories at customer vendor managed locations is not recognized until the products are pulled from consignment inventories by customers. In instances where acceptance of the product or solutions is specified by the customer, revenue is deferred until such required acceptance criteria have been met. Shipping and handling costs are included in the cost of goods sold. The Company presents revenue net of sales taxes and any similar assessments. Nature of products Revenue from sale of hardware products is recognized upon transfer of control to the customer. The performance obligation for the sale of hardware products is satisfied at a point in time. The Company has aligned its products in two groups - High Speed Products and Network Products and Solutions. The following presents revenue by product group (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 High Speed Products $ 68,519 $ 59,426 $ 197,362 $ 177,488 Network Products and Solutions 13,229 11,695 34,074 38,535 Total revenue $ 81,748 $ 71,121 $ 231,436 $ 216,023 The following table presents the Company's revenue information by geographical region. Revenue is classified based on the ship to location requested by the customer. Such classification recognizes that for many customers, including those in North America or in Europe, designated shipping points are often in China or elsewhere in Asia (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 China $ 46,134 $ 40,513 $ 133,917 $ 117,599 Americas 22,369 13,487 52,270 36,853 Rest of world 13,245 17,121 45,249 61,571 Total revenue $ 81,748 $ 71,121 $ 231,436 $ 216,023 Certain prior period amounts have been reclassified to conform to the current period presentation. Deferred revenue The Company records deferred revenue when cash payments are received or due in advance of our performance. Refer to Note 7 for disclosure of deferred revenue balances. The increase in the deferred revenue balances during the three and nine months ended September 30, 2018 was immaterial, offset by approximately $0.2 million and $0.8 million of revenue recognized during the three and nine months ended September 30, 2018 that was included in the deferred revenue balance as of December 31, 2017. The increase in the deferred revenue balances during the three and nine months ended September 30, 2017 was $0.1 million and $1.7 million , respectively, offset by approximately $0.2 million and $0.7 million of revenue recognized during the three and nine months ended September 30, 2017, respectively, that was included in the deferred revenue balance as of December 31, 2016. Contract assets The Company records contract assets when the revenue is recognized but the customer payment is contingent on a future event. The balance of contract assets as of September 30, 2018 and December 31, 2017 was immaterial. Refund liabilities The Company records refund liabilities when the contract permits the customer to return the product if certain circumstances arise. The balance of refund liabilities as of September 30, 2018 and December 31, 2017 was immaterial.

Net loss per share

Net loss per share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Net loss per share	Net loss per share The following table sets forth the computation of the basic and diluted net loss per share for the periods indicated (in thousands, except per share amounts): Three Months Ended Nine Months Ended 2018 2017 2018 2017 Numerator: Net loss $ (8,125 ) $ (18,187 ) $ (36,908 ) $ (39,050 ) Denominator: Weighted average shares used to compute per share amount: Basic 45,476 43,790 44,804 43,212 Diluted 45,476 43,790 44,804 43,212 Basic net loss per share $ (0.18 ) $ (0.42 ) $ (0.82 ) $ (0.90 ) Diluted net loss per share $ (0.18 ) $ (0.42 ) $ (0.82 ) $ (0.90 ) The Company has excluded the impact of the following outstanding employee stock options and restricted stock units as well as the shares expected to be issued under its employee stock purchase plan from the computation of diluted net loss per share, as their effect would have been antidilutive (in thousands): September 30, 2018 September 30, 2017 Employee stock options 3,405 4,227 Restricted stock units 2,630 2,504 Market-based restricted stock units 665 — Employee stock purchase plan 174 245 6,874 6,976

Cash, cash equivalents, short-t

Cash, cash equivalents, short-term investments, and restricted cash	9 Months Ended
	Sep. 30, 2018
Cash and Cash Equivalents [Abstract]
Cash, cash equivalents, short-term investments, and restricted cash	Cash, cash equivalents, short-term investments, and restricted cash The following table summarizes the Company’s cash, cash equivalents, short-term investments and restricted cash (in thousands): September 30, December 31, Cash and cash equivalents: Cash $ 52,099 $ 78,906 Cash equivalents — — Cash and cash equivalents $ 52,099 $ 78,906 Short-term investments $ 7,441 $ 12,311 Restricted cash $ 5,195 $ 2,658 September 30, December 31, Cash and cash equivalents $ 52,099 $ 78,906 Restricted cash 5,195 2,658 Total cash, cash equivalents and restricted cash shown in the statement of cash flows $ 57,294 $ 81,564 As of September 30, 2018 restricted cash primarily included approximately $2.1 million pursuant to an asset purchase agreement with APAT Optoelectronics Components Co., Ltd. (“APAT OE”) relating to the asset sale closed in January 2017, approximately $1.2 million relating to government grants received in advance and approximately $1.9 million for the compensating balances relating to the Company’s notes payable issued under its line of credit facilities in China (see Note 9). As of December 31, 2017, restricted cash primarily included approximately $2.1 million pursuant to an asset purchase agreement with APAT OE. The following table summarizes the Company’s unrealized gains and losses related to its cash equivalents and short-term investments in marketable securities designated as available-for-sale (in thousands): As of September 30, 2018 As of December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Loss Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Loss Fair Value Marketable securities: Money market funds $ 7,441 $ — $ — $ 7,441 $ 11,561 $ — $ — $ 11,561 U.S. government securities — — — — 751 — (1 ) 750 Total $ 7,441 $ — $ — $ 7,441 $ 12,312 $ — $ (1 ) $ 12,311 Reported as: Short-term investments 7,441 — — 7,441 12,312 — (1 ) 12,311 Total $ 7,441 $ — $ — $ 7,441 $ 12,312 $ — $ (1 ) $ 12,311 As of September 30, 2018 and December 31, 2017 , maturities of marketable securities were as follows (in thousands): September 30, December 31, Less than 1 year $ 7,441 $ 12,311 Due in 1 to 2 years — — Due in 3 to 5 years — — Total $ 7,441 $ 12,311 Realized gains and losses on the sale of marketable securities during the three and nine months ended September 30, 2018 and 2017 were insignificant. The Company did not recognize any impairment losses on its marketable securities during the three and nine months ended September 30, 2018 or 2017 . As of September 30, 2018 , the Company did not have any investments in marketable securities that were in an unrealized loss position for a period in excess of 12 months.

Fair value disclosures

Fair value disclosures	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair value disclosures	Fair value disclosures Assets and Liabilities Measured at Fair Value on a Recurring Basis The following table presents the Company's assets that are measured at fair value on a recurring basis (in thousands): As of September 30, 2018 As of December 31, 2017 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Cash equivalents and short-term investments: Money market funds $ 7,441 $ — $ — $ 7,441 $ 11,561 $ — $ — $ 11,561 U.S. government securities — — — — 750 — — 750 Total $ 7,441 $ — $ — $ 7,441 $ 12,311 $ — $ — $ 12,311 Foreign currency forward contracts* $ — $ — $ — $ — $ — $ — $ — $ — Mutual funds held in Rabbi Trust, recorded in other long-term assets $ 569 $ — $ — $ 569 $ 523 $ — $ — $ 523 ________________________________________________________ *The fair value of the Company’s foreign currency forward contract was immaterial as of December 31, 2017. The Company offers a Non-Qualified Deferred Compensation Plan (“NQDC Plan”) to a select group of its highly compensated employees. The NQDC Plan provides participants the opportunity to defer payment of certain compensation as defined in the NQDC Plan. A Rabbi Trust has been established to fund the NQDC Plan obligation, which was fully funded at September 30, 2018 . The assets held by the Rabbi Trust are substantially in the form of exchange traded mutual funds and are included in the Company’s other long-term assets on its condensed consolidated balance sheets as of September 30, 2018 and December 31, 2017 . Effective July 1, 2016, the Company maintains a hedging program using forward exchange contracts as economic hedges, to protect against volatility of foreign exchange rate exposure when it is deemed economical to do so, based on a cost-benefit analysis that considers the magnitude of the exposure, the volatility of the exchange rate and the cost of the hedging instrument. The forward contracts are not designated for hedge accounting. Under the hedging program, the Company enters into monthly forward exchange contracts, that have average maturities of one month , to offset the effects of exchange rate exposures for its net intercompany activities denominated in Chinese Renminbi, or RMB, by buying and selling the underlying foreign currency in the future at fixed exchange rates, to offset the consequences of changes in foreign exchange on the balance sheet. Accordingly, fair value changes in the forward contracts help mitigate the changes in the value of the re-measurement of the hedged assets and liabilities attributable to changes in foreign currency exchange rates, except to the extent of the spot-forward differences. The net effect of fair value changes is reported in other income (expense), net. The Company temporarily discontinued entering into forward exchange contracts in the quarter ended September 30, 2018, as it was uneconomical for the Company to enter into forward exchange contracts. The following table presents the Company's liabilities that are measured at fair value on a recurring basis (in thousands): As of September 30, 2018 As of December 31, 2017 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Rusnano payment derivative $ — $ — $ 2,000 $ 2,000 $ — $ — $ 389 $ 389 Foreign currency forward contracts — — — — — 43 — 43 $ — $ — $ 2,000 $ 2,000 $ — $ 43 $ 389 $ 432 Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis As of September 30, 2018 and December 31, 2017 the Company had no assets or liabilities required to be measured at fair value on a nonrecurring basis. In the three months ended March 31, 2017, the Company recorded a $6.7 million contingent liability within accrued and other current liabilities on its balance sheet in connection with the contingent indemnification commitments pursuant to an asset sale closed in January 2017. See Note 6. This liability was measured using the Company's best estimate of the likelihood of payment based on circumstances the Company identified as having a significant impact on its fair value during the period, which is considered to be a level 3 fair value measurement. Assets and Liabilities Not Measured at Fair Value The carrying values of accounts receivable, accounts payable, notes payable and short-term borrowings approximate their fair values due to the short-term nature and liquidity of these financial instruments. The estimated fair value of the Company's long-term debt approximated its carrying value as of September 30, 2018 and December 31, 2017 , as the interest rates approximated rates currently available to the Company on the issuance of liabilities with a similar maturity. This estimate is considered to be a level 2 fair value measurement.

Asset sale

Asset sale	9 Months Ended
	Sep. 30, 2018
Discontinued Operations and Disposal Groups [Abstract]
Asset sale	Asset sale In January 2017, the Company completed the sale of its Low Speed Transceiver Products’ assets to APAT OE pursuant to an asset purchase agreement dated December 14, 2016 for consideration of approximately $25.0 million (in RMB equivalent) plus approximately $1.4 million (in RMB equivalent) for post-closing transaction service fees under a transition services agreement with APAT OE in which the Company provided short-term manufacturing and other specific services pursuant to such agreement. The related supply chain purchase commitments and value-added tax obligations have been assumed by APAT OE. The receivable and payable balances related to the transition service arrangement were $12.1 million and $11.8 million , respectively, as of September 30, 2018 . See Note 11 for litigation and arbitration matters with APAT OE. As of December 31, 2016, the balance in assets held for sale was $13.9 million , consisting of $13.1 million in inventories and $0.8 million in property, plant and equipment. As a result of post-closing adjustments, total consideration was reduced by approximately $3.4 million for inventory. In addition, an immaterial amount of property, plant and equipment was reclassified from assets held for sale. Upon closing, assets sold to APAT OE were approximately $12.8 million , including approximately $12.1 million in inventories and $0.7 million in property, plant and equipment. The adjusted consideration received of approximately $21.6 million is subject to further reduction of up to $10.0 million for any indemnification claims. As of September 30, 2018 , the Company has a reserve of $6.8 million within accrued and other current liabilities for warranty claims. The indemnification warranties expired on June 30, 2017. The Company recognized a $2.2 million gain on the sale of these assets within the operating loss in 2017. All of the Low Speed Transceiver Products were part of the Company’s Network Products and Solution product group and included the low speed optical network (PON) products for which the end-of-life plan was announced in mid-2016.

Balance sheet components

Balance sheet components	9 Months Ended
	Sep. 30, 2018
Balance Sheet Related Disclosures [Abstract]
Balance sheet components	Balance sheet components Accounts receivable, net Accounts receivable, net, consists of the following (in thousands): September 30, 2018 December 31, 2017 Accounts receivable $ 66,264 $ 65,499 Trade notes receivable 476 2,356 Allowance for doubtful accounts (120 ) (626 ) $ 66,620 $ 67,229 Inventories, net Inventories, net consist of the following (in thousands): September 30, 2018 December 31, 2017 Raw materials $ 26,904 $ 33,400 Work in process 11,755 13,246 Finished goods (1) 18,465 20,655 $ 57,124 $ 67,301 ________________________________________________________ (1) Finished goods inventory at customer vendor managed inventory locations was $6.8 million and $7.1 million as of September 30, 2018 and December 31, 2017 , respectively. Assets held for sale In September 2018, the Company received a non binding term sheet from Joint Stock Company Rusnano, a related party, for Joint Stock Company Rusnano group to purchase the 100% interest in the operations of NeoPhotonics Corporation, LLC, the Company's manufacturing operations in Russia. In the three and nine months ended September 30, 2018, the Company recorded additional restructuring expense of $1.0 million and $1.6 million , respectively for the Rusnano payment derivative related to these operations. As of September 30, 2018, the Company reclassified assets with carrying value of $3.2 million as held for sale primarily consisting of $2.6 million of property, plant and equipment and $0.6 million of prepaid expenses and other current assets. The estimated fair value less direct costs of sale approximates the related carrying value. The balance for liabilities held for sale as of September 30, 2018 was immaterial and was primarily included in accrued and other current liabilities. Prepaid expenses and other current assets Prepaid expenses and other current assets consist of the following (in thousands): September 30, 2018 December 31, 2017 Prepaid taxes and taxes receivable $ 7,167 $ 15,162 Transition services agreement receivable (Note 6) 12,120 12,817 Deposits and other prepaid expenses 3,975 4,138 Other receivable 5,397 4,118 $ 28,659 $ 36,235 Property, plant and equipment, net Purchases of property, plant and equipment unpaid as of September 30, 2018 and September 30, 2017 was $1.1 million and $9.7 million , respectively. Purchased intangible assets Purchased intangible assets consist of the following (in thousands): September 30, 2018 December 31, 2017 Gross Assets Accumulated Amortization Net Assets Gross Accumulated Net Technology and patents $ 37,045 $ (34,833 ) $ 2,212 $ 37,684 $ (34,923 ) $ 2,761 Customer relationships 15,123 (14,888 ) 235 15,425 (14,835 ) 590 Leasehold interest 1,240 (367 ) 873 1,309 (366 ) 943 $ 53,408 $ (50,088 ) $ 3,320 $ 54,418 $ (50,124 ) $ 4,294 Amortization expense relating to technology and patents and the leasehold interest intangible assets is included within cost of goods sold and customer relationships within operating expenses. The following table presents details of the amortization expense of the Company’s purchased intangible assets as reported in the condensed consolidated statements of operations (in thousands): Three Months Ended Nine Months Ended 2018 2017 2018 2017 Cost of goods sold $ 185 $ 202 $ 572 $ 667 Operating expenses 118 119 357 355 Total $ 303 $ 321 $ 929 $ 1,022 The estimated future amortization expense of purchased intangible assets as of September 30, 2018 , is as follows (in thousands): 2018 (remaining three months) $ 302 2019 855 2020 737 2021 645 2022 28 Thereafter 753 $ 3,320 Accrued and other current liabilities Accrued and other current liabilities consist of the following (in thousands): September 30, 2018 December 31, 2017 Transition services agreement payables (Note 6) $ 11,769 $ 11,222 Employee-related 14,742 12,990 Asset sale related contingent liabilities (Note 6) 6,760 7,135 Accrued warranty 1,199 1,334 Deferred revenue, current 704 939 Income and other taxes payable 2,376 542 Rusnano payment derivative 2,000 — Other accrued expenses 7,307 9,080 $ 46,857 $ 43,242 Warranty Accrual The table below summarizes the movement in the warranty accrual, which is included in accrued and other current liabilities (in thousands): Three Months Ended Nine Months Ended 2018 2017 2018 2017 Beginning balance $ 1,592 $ 528 $ 1,334 $ 678 Warranty accruals (42 ) 1,047 487 1,019 Settlements (351 ) (173 ) (622 ) (295 ) Ending balance $ 1,199 $ 1,402 $ 1,199 $ 1,402 Other noncurrent liabilities Other noncurrent liabilities consist of the following (in thousands): September 30, 2018 December 31, 2017 Pension and other employee-related $ 4,651 $ 4,675 Deferred rent 3,023 2,908 Deferred revenue 112 617 Government grant 1,912 1,095 Rusnano payment derivative — 389 Deferred income tax liabilities 63 106 Asset retirement obligations and other 3,627 4,285 $ 13,388 $ 14,075

Restructuring

Restructuring	9 Months Ended
	Sep. 30, 2018
Restructuring and Related Activities [Abstract]
Restructuring	Restructuring In 2017, the Company initiated restructuring actions in order to focus on key growth initiatives and to move towards a lower break even revenue level through lower operating expenses and manufacturing cost reductions. Actions included a reduction in force, facilities consolidation and certain asset-related adjustments. The Company recorded $0.1 million and $0.2 million in restructuring charges within cost of goods sold in the three and nine months ended September 30, 2018 , respectively, and $1.1 million and $1.8 million in restructuring charges within operating expenses in the three and nine months ended September 30, 2018, respectively. The Company recorded $3.1 million and $4.1 million in restructuring charges within cost of goods sold and operating expenses in the three and nine months ended September 30, 2017. Restructuring activities for the nine months ended September 30, 2018 were as follows (in thousands): Employee Severance Facilities Consolidation Others Total Restructuring obligations December 31, 2017 $ — $ 1,580 $ 43 $ 1,623 Charges 269 — 1,704 1,973 Cash payments (147 ) (640 ) (43 ) (830 ) Non-cash settlements and others — — (94 ) (94 ) Restructuring obligations September 30, 2018 $ 122 $ 940 $ 1,610 $ 2,672 The current restructuring liability reported in Accrued and other current liabilities in the Condensed Consolidated Balance Sheets as of September 30, 2018 was $2.6 million . The non-current restructuring liability reported in other noncurrent liabilities in the Condensed Consolidated Balance Sheets as of September 30, 2018 was $0.1 million .

Debt

Debt	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Debt	Debt The table below summarizes the carrying amount and weighted average interest rate of the Company’s debt (in thousands, except percentages): September 30, 2018 December 31, 2017 Carrying Amount Interest Rate Carrying Interest Note payable to Shanghai Pudong Development Bank $ — $ 17,000 4.10 % Note payable to China CITIC Bank — 17,000 4.00 % Notes payable to suppliers 3,634 — 1,607 Total notes payable and short-term borrowing $ 3,634 $ 35,607 Long-term debt, current and non-current: Borrowing under Wells Fargo Credit Facility $ 35,630 4.51 % $ 30,018 3.29 % Mitsubishi Bank loans 11,206 1.05% -1.45% 16,924 1.05% -1.45% Mitsubishi Bank and Yamanashi Chou Bank loan 6,942 1.1 % — Unaccreted discount and issuance costs within current portion of long-term debt (161 ) (86 ) Unaccreted discount and issuance costs within long-term debt, net of current portion (463 ) (295 ) Total long-term debt, net of unaccreted discount and issuance costs $ 53,154 $ 46,561 Reported as: Current portion of long-term debt $ 2,798 $ 6,005 Long-term debt, net of current portion 50,356 40,556 Total long-term debt, net of unaccreted discount and issuance costs $ 53,154 $ 46,561 Notes payable and short-term borrowing The Company regularly issues notes payable to its suppliers in China. These notes are supported by non-interest bearing bank acceptance drafts issued under the Company’s existing line of credit facilities and are due three to six months after issuance. As a condition of the notes payable arrangements, the Company is required to keep a compensating balance at the issuing banks that is a percentage of the total notes payable balance until the amounts are settled. As of September 30, 2018 , the Company’s subsidiary in China had three line of credit facilities with the following banking institutions: • Under the first line of credit facility with Shanghai Pudong Development Bank, the Company can borrow up to RMB 120.0 million ( $17.5 million ) for short-term loans at varying interest rates, or up to approximately RMB 240.0 million ( $34.9 million ) for bank acceptance drafts (with up to 50% compensating balance requirement). This line of credit facility expires in July 2019. In November 2017, the Company borrowed $17.0 million under this line which bore interest at 4.1% . The amount of $17.0 million under this line was repaid in May 2018. • Under the second line of credit facility with Shanghai Pudong Development Bank, which expires in July 2019, the Company can borrow up to RMB 30.0 million ( $4.4 million ) for short-term loans at varying interest rates, or up to approximately RMB 60.0 million ( $8.7 million ) for bank acceptance drafts (with up to 50% compensating balance requirement). • In December 2017, the Company's subsidiary in China entered into a third line of credit facility with China CITIC Bank in China, which expires in November 2018. The purpose of the credit facility is to provide short-term borrowings, bank acceptance drafts and letters of credits. Under this credit facility, the Company can borrow up to approximately RMB 250 million ( $36.4 million ) at varying interest rates, or up to approximately RMB 390.6 million ( $56.9 million ) for bank acceptance drafts (with up to 36% compensating balance requirement). In February 2018, the Company borrowed $17.0 million under this line which bore interest at 4.7% . The amount of $17.0 million under this line was repaid in August 2018. The Company had a line of credit facility previously with China CITIC Bank in China which expired during September 2017. In July 2017, the Company borrowed $17.0 million under this line which bears interest at LIBOR plus 2.55% . The amount of $17.0 million under this line was repaid to CITIC Bank in January 2018. Under these line of credit facilities, the non-interest bearing bank acceptance drafts issued in connection with the Company’s notes payable to its suppliers in China, had an outstanding balance of $3.6 million and $1.6 million as of September 30, 2018 and December 31, 2017 , respectively. In addition to the outstanding notes payable, three letters of credit totaling $1.6 million were issued to its suppliers in 2016 for equipment purchases delivered by December 2016. These letters of credit required a 30% compensating balance. As of December 31, 2016, the outstanding balance of these letters of credit was immaterial and was fully repaid as of December 31, 2017. As of September 30, 2018 and December 31, 2017 , compensating balances relating to these bank acceptance drafts and letters of credit issued to suppliers and the Company’s subsidiaries totaled $1.9 million and $0.5 million , respectively. Compensating balances are classified as restricted cash on the Company’s condensed consolidated balance sheets. In China, when there is a case pending in judicial court, banks may choose to limit borrowing against existing credit lines, regardless of the legitimacy of the case. The Company has a dispute pending with APAT OE in judicial court (See Note 11). The Company does not expect to make any additional draws against its credit facilities in China until this matter is resolved. Credit facilities The Company had a credit agreement, as amended, with Comerica Bank as lead bank in the U.S. (the “Comerica Bank Credit Facility”) with a borrowing capacity of up to $30.0 million . In January 2017, the Company amended the Comerica Bank Credit Facility to extend the maturity to April 30, 2017 and to remove the covenant related to EBITDA. In April 2017, the Company amended the Comerica Bank Credit Facility to extend the maturity date to July 31, 2017 and to add a financial covenant that required maintenance of a modified EBITDA. In June 2017, the Company amended the Comerica Bank Credit Facility to extend the maturity to August 31, 2017, to allow NeoPhotonics China to borrow up to $17.0 million , to limit the indebtedness under the facility to $20.0 million and to modify the EBITDA requirement. In August 2017, the Credit Facility was further amended to extend the maturity to September 30, 2017. Borrowings under the Comerica Bank Credit Facility bore interest at an interest rate option of a base rate as defined in the agreement plus 1.75% or LIBOR plus 2.75% . The base rate was the greater of (a) the effective prime rate, (b) the Federal Funds effective rate plus one percent, and (c) the daily adjusting LIBOR rate plus one percent. In September 2017, the Company entered into a revolving line of credit agreement with Wells Fargo Bank, National Association ("Wells Fargo") as the administrative agent for a lender group (the "Wells Fargo Credit Facility" or "Credit Facility"), and the amount outstanding under the Comerica Bank Credit Facility was paid in full. The Wells Fargo Credit Facility provides for borrowings equal to the lower of (a) a maximum revolver amount of $50.0 million , or (b) an amount equal to 80% - 85% of eligible accounts receivable plus 100% of qualified cash balances up to $15.0 million , less certain discretionary adjustments ("Borrowing Base"). The maximum revolver amount may be increased by up to $25.0 million , subject to certain conditions. At closing, $50.0 million was available, of which $30.0 million was drawn. The Company used $20.0 million of this amount to pay the principal and interest due under the Comerica Bank Credit Facility, which has since been terminated. The Credit Facility matures on June 30, 2022 and borrowings bear interest at an interest rate option of either (a) the LIBOR rate, plus an applicable margin ranging from 1.50% to 1.75% per annum, or (b) the prime lending rate, plus an applicable margin ranging from 0.50% to 0.75% per annum. The Company is also required to pay a commitment fee equal to 0.25% of the unused portion of the Credit Facility. The Credit Facility agreement ("Agreement") requires prepayment of the borrowings to the extent the outstanding balance is greater than the lesser of (a) the most recently calculated Borrowing Base, or (b) the maximum revolver amount. The Company is required to maintain a combination of certain defined cash balances and unused borrowing capacity under the Credit Facility of at least $20.0 million , of which at least $5.0 million shall include unused borrowing capacity. The Agreement also restricts the Company's ability to dispose of assets, permit change in control, merge or consolidate, make acquisitions, incur indebtedness, grant liens, make investments and make certain restricted payments. Borrowings under the Credit Facility are collateralized by substantially all of the Company's assets. The Company was in compliance with the covenants of this Credit Facility as of September 30, 2018 . As of September 30, 2018 , the outstanding balance under the Credit Facility was $35.6 million and the weighted average rate under the LIBOR option was 4.51% . The remaining borrowing capacity as of September 30, 2018 was $14.4 million , of which $5.0 million is required to be maintained as unused borrowing capacity. The Company repaid $5.0 million in October 2018, which was borrowed in September 2018. Mitsubishi Bank loans On February 25, 2015, the Company entered into certain loan agreements and related agreements with the Bank of Tokyo-Mitsubishi UFJ, Ltd. (the “Mitsubishi Bank”) that provided for (i) a term loan in the aggregate principal amount of 500 million JPY ( $4.4 million ) (the “Term Loan A”) and (ii) a term loan in the aggregate principal amount of one billion JPY ( $8.8 million ) (the “Term Loan B” and together with the Term Loan A, the “2015 Mitsubishi Bank Loans”). The Mitsubishi Bank Loans are secured by a mortgage on certain real property and buildings owned by the Company’s Japanese subsidiary. Interest on the 2015 Mitsubishi Bank Loans accrues and is paid monthly based upon the annual rate of the monthly Tokyo Interbank Offer Rate (TIBOR) plus 1.40% . The Term Loan A required interest only payments until the maturity date of February 23, 2018, with a lump sum payment of the aggregate principal amount on the maturity date. The Term Loan B requires equal monthly payments of principal equal to 8,333,000 JPY until the maturity date of February 25, 2025, with a lump sum payment of the balance of 8,373,000 JPY on the maturity date. Interest on the Term Loan B is accrued based upon monthly TIBOR plus 1.40% and is secured by real estate collateral. In conjunction with the execution of the Bank Loans, the Company paid a loan structuring fee, including consumption tax, of 40,500,000 JPY ( $0.4 million ). The Term Loan A of 500 million JPY (approximately $4.4 million ) was repaid to the Mitsubishi Bank in January 2018. The 2015 Mitsubishi Bank Loans contain customary representations and warranties and customary affirmative and negative covenants applicable to the Company’s Japanese subsidiary, including, among other things, restrictions on cessation in business, management, mergers or acquisitions. The 2015 Mitsubishi Bank Loans contain financial covenants relating to minimum net assets, maximum ordinary loss and a dividends covenant. Outstanding principal balance for Term Loan B and unamortized debt issuance costs were approximately 641.7 million JPY (approximately $5.6 million ) and 71.0 million JPY (approximately $0.6 million ), respectively, as of September 30, 2018 . The Company was in compliance with the related covenants as of September 30, 2018 and December 31, 2017 . In March 2017, the Company entered into a loan agreement and related agreements with the Mitsubishi Bank for a term loan of 690 million JPY (approximately $6.1 million ) (the “2017 Mitsubishi Bank Loan”) to acquire manufacturing equipment for its Japanese subsidiary. This loan is secured by the manufacturing equipment acquired from the loan proceeds. Interest on the 2017 Mitsubishi Bank Loan is based on the annual rate of the monthly TIBOR rate plus 1.00% . The 2017 Mitsubishi Bank Loan matures on March 29, 2024 and requires monthly interest and principal payments over 72 months commencing in April 2018. The loan contains customary covenants relating to minimum net assets, maximum ordinary loss and a dividends covenant. The Company was in compliance with these covenants as of September 30, 2018. The loan was available from March 31, 2017 to March 30, 2018 and 690 million JPY (approximately $6.1 million ) under this loan was fully drawn in March 2017. Mitsubishi Bank and Yamanashi Chou Bank loan In January 2018, the Company entered into a term loan agreement with Mitsubishi Bank and The Yamanashi Chou Bank, Ltd. for a term loan in the aggregate principal amount of 850 million JPY (approximately $7.5 million ) (the “Term Loan C”). The purpose of the Term Loan C is to obtain machinery for the core parts of the manufacturing line and payments for related expenses by the Company's subsidiary in Japan. The Term Loan C is secured by the assets owned by the Company's subsidiary in Japan. The Term Loan C was available from January 29, 2018 to January 29, 2025. The full amount of the Term Loan C was drawn in January 2018. Interest on the Term Loan C is based upon the annual rate of the three months TIBOR rate plus 1.00% . The Term Loan C requires quarterly interest payments, along with the principal payments, over 82 months commencing in April 2018. The Term Loan C loan agreement contains customary representations and warranties and customary affirmative and negative covenants applicable to the Japanese Subsidiary, including, among other things, restrictions on cessation in business, management, mergers or acquisitions. The Term Loan C loan agreement contains financial covenants relating to minimum net assets and maximum ordinary loss. The Company was in compliance with these covenants as of September 30, 2018. As of September 30, 2018 , maturities of total long-term debt were as follows (in thousands): 2018 (remaining three months) $ 740 2019 2,959 2020 2,959 2021 2,959 2022 38,589 Thereafter 5,572 $ 53,778

Japan pension plan

Japan pension plan	9 Months Ended
	Sep. 30, 2018
Retirement Benefits [Abstract]
Japan pension plan	Japan pension plan The pension liability related to the Company’s Retirement Allowance Plan (“RAP”) in Japan as of September 30, 2018 was $4.1 million which was recorded in other noncurrent liabilities on the Company’s condensed consolidated balance sheet. The pension liability related to the Company’s RAP in Japan as of December 31, 2017 was $4.6 million , of which $0.5 million , was recorded in accrued and other current liabilities and the remainder in other noncurrent liabilities on the Company’s condensed consolidated balance sheet. Net periodic pension cost associated with this plan was immaterial in the three and nine months ended September 30, 2018 and 2017 .

Commitments and contingencies

Commitments and contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and contingencies	Commitments and contingencies Litigation From time to time, the Company is subject to various claims and legal proceedings, either asserted or unasserted, that arise in the ordinary course of business. The Company accrues for legal contingencies if the Company can estimate the potential liability and if the Company believes it is probable that the case will be ruled against it. If a legal claim for which the Company did not accrue is resolved against it, the Company would record the expense in the period in which the ruling was made. The Company believes that the likelihood of an ultimate amount of liability, if any, for any pending claims of any type (alone or combined) that will materially affect the Company’s financial position, results of operations or cash flows is remote. The ultimate outcome of any litigation is uncertain, however, and unfavorable outcomes could have a material negative impact on the Company’s financial condition and operating results. Regardless of outcome, litigation can have an adverse impact on the Company because of defense costs, negative publicity, diversion of management resources and other factors. On January 5, 2010, Finisar Corporation, or Finisar, filed a complaint in the U.S. District Court for the Northern District of California, or the Court, against Source Photonics, Inc., MRV Communications, Inc., Oplink Communications, Inc. and the Company, or collectively, the co-defendants. In the complaint Finisar alleged infringement of certain of its U.S. patents. In 2010 the Company filed an answer to the complaint and counterclaims, asserting two claims of patent infringement and additional claims. The Court dismissed without prejudice all co-defendants (including the Company) except Source Photonics, Inc., on grounds that such claims should have been asserted in four separate lawsuits, one against each defendant. This dismissal does not prevent Finisar from bringing a new similar lawsuit against the Company. In 2011 the Company and Finisar agreed to suspend their respective claims and in 2012 the Company and Finisar further agreed to toll their respective claims. While there has been no action on this matter since 2012, the Company is currently unable to predict the outcome of this dispute and therefore cannot determine the likelihood of loss nor estimate a range of possible loss. On December 27, 2016 the Company was served with a lawsuit filed by Lestina International Ltd. (“Lestina”), in Santa Clara County, CA. The lawsuit is regarding a dispute of approximately $3.0 million related to purchase orders for the Company’s Low Speed Transceiver Products that was soon thereafter sold by the Company to APAT OE in January 2017. The purchase orders in question were included in the asset sale and were assumed liabilities by the purchaser of the business. The Company is unable to predict with certainty the outcome of this matter, but is seeking to resolve the matter either through a court dismissal of the action or a resolution with the plaintiff and/or the purchaser of the Low Speed Transceiver Products’ assets. Discovery is currently in process. Because the purchase orders in question were an assumed liability of the Low Speed Transceiver Products’ assets that were transferred to the purchaser, the Company does not expect that the ultimate costs to resolve these matters will have a material adverse effect on its consolidated financial position, results of operations or cash flows. A trial date is currently scheduled for January 14, 2019. On April 21, 2018, APAT OE filed a lawsuit in the Qianhai Court in Shenzhen, China against NeoPhotonics (China) Co., Ltd. ("NeoChina"), NeoPhotonics Corporation and NeoPhotonics Dongguan Co. Ltd. The lawsuit is in reference to the sale of the low speed transceiver business to APAT OE from NeoChina. APAT OE claims that the business has been losing money and that APAT OE was not given all of the information about the business they purchased prior to signing the Asset Purchase Agreement. On May 28, 2018, counsel on behalf of NeoChina filed a motion objecting to the jurisdiction, claiming that the proper jurisdiction for any dispute between these parties is the Shenzhen Court of International Arbitration and the proper parties to this dispute are NeoChina and APAT OE, pursuant to the Asset Purchase Agreement signed by APAT OE and NeoChina. On June 20, 2018 a hearing was held in the Qianhai Court in Shenzhen, China. The Court ruled in favor of APAT OE. NeoChina has filed an appeal which will be heard in the Intermediate Court of Shenzhen; however, a court date has not yet been scheduled. On October 10, 2018, a hearing was held in the Intermediate Court of Shenzhen which was filed by NeoChina. At that hearing arguments were heard regarding the proper jurisdiction for all disputes between NeoChina and APAT OE. NeoChina argued that all disputes between the parties should be decided in the Shenzhen Court of Arbitration per the Asset Purchase Agreement between the parties. APAT OE argued that the Qianhai Court is the appropriate jurisdiction. The Company is unable to predict the outcome of this matter. APAT Arbitration On June 16, 2017, APAT OE filed an arbitration claim against NeoChina (the Company’s China subsidiary), claiming that approximately $1.5 million of the inventory that was sold to APAT OE by NeoChina in an Asset Purchase Agreement executed between the parties on December 14, 2016 was aged inventory and of no value. The arbitration was heard in the Shenzhen Court of International Arbitration on August 2, 2017. On October 25, 2017, NeoChina was informed that it was successful in the defense of the dispute and was also successful in its counterclaim against APAT OE. NeoChina was awarded approximately RMB 700,000 (approximately USD $110,000 ) in compensatory damages and attorney fees as well as having the approximately $1.5 million claim against it rejected in its entirety. On or about May 1, 2018, APAT OE filed a Notice of Judicial Review of the arbitration judgment in the Shenzhen Intermediate Court in Shenzhen, China. The case was heard on May 29, 2018, and NeoChina was successful in disputing the Judicial Review, which means that the arbitration judgment against APAT OE and in favor of NeoChina stands. Although APAT OE continues to dispute this matter through the lawsuit as described in the above litigation section, the Company and its affiliates continue to argue that the proper jurisdiction for any dispute in reference to the low speed transceiver business purchased by APAT OE is the Shenzhen Court of International Arbitration. Indemnifications In the normal course of business, the Company enters into agreements that contain a variety of representations and warranties and provide for general indemnification. The Company’s exposure under these agreements is unknown because it involves claims that may be made against the Company in the future, but have not yet been made. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. However, the Company may record charges in the future as a result of these indemnification obligations. In November 2016, Oyster Communications, Inc. filed nine patent lawsuits against several defendants in the U.S. District Court for the Eastern District of Texas, including one against Cisco Systems, Inc. ("Cisco"). One defendant successfully transferred their case to the U.S. District Court for the Northern District of California. Additional defendants requested venue changes are still pending. The Company was not named as a defendant in any of the lawsuits. In July 2017, Cisco notified the Company that it would be seeking indemnification from the Company for claims against Cisco arising from the lawsuits and the parties engaged in discussions and negotiations. In September 2018, the Company and Cisco signed a settlement agreement under which the Company agreed to pay to Cisco $300,000 to be paid by January 31, 2019 and $150,000 in product credits to be applied during calendar year 2019. This settlement resolves Cisco's indemnification claims against the Company in this matter. Leases The Company leases various facilities under non-cancelable operating leases expiring through 2027. As of September 30, 2018 , future minimum payments under these operating leases totaled approximately $27.8 million and future minimum sublease receipts were approximately $1.4 million . Rent expense was $1.1 million and $3.2 million in the three and nine months ended September 30, 2018 and $1.3 million and $3.5 million in the three and nine months ended September 30, 2017 . On June 13, 2017, the Company entered into an office lease for approximately 39,000 square feet for the Company’s current headquarters in San Jose, California (the “2017 Lease”) with a commencement date of June 1, 2017. The Company’s existing office lease for the facility was terminated and replaced by the 2017 Lease. Upon commencement, the 2017 Lease had an initial term of one hundred and twenty-three ( 123 ) months, ending September 30, 2027, (the “02017 Lease Initial Term”) with a monthly rental rate of $41,388 , escalating annually to a maximum monthly rental rate of approximately $72,525 in the last year of the 2017 Lease Initial Term. Upon termination of the 2017 Lease, the Company anticipates a restoration cost of approximately $0.7 million . In September 2016, the Company entered into an office lease for approximately 64,000 square feet of office and laboratory space located adjacent to the Company’s current headquarters in San Jose, California (the “2016 Lease”). The term of the 2016 Lease commenced on January 1, 2017. Upon commencement, the 2016 Lease has an initial term of one hundred and twenty-nine ( 129 ) months, ending on September 30, 2027 (the “2016 Lease Initial Term”), with a monthly rental rate of $144,000 , escalating annually to a maximum monthly rental rate of approximately $194,000 in the last year of the 2016 Lease Initial Term. The Landlord has agreed to provide the office and laboratory space to the Company free of charge for the first nine months of the 2016 Lease Initial Term through September 30, 2017. Upon termination of the 2016 Lease, the Company anticipates a restoration cost of approximately $3.1 million . Penalty Payment Derivative In connection with a private placement transaction with Joint Stock Company “Rusnano” (formerly Open Joint Stock Company “RUSNANO”), or Rusnano, in 2012, the Company agreed to certain performance obligations including establishing a wholly-owned subsidiary in Russia and making a $30.0 million investment commitment (the “Investment Commitment’) towards the Company’s Russian operations, which could be partially satisfied by cash and/or non-cash investment inside or outside of Russia and/or by way of non-cash asset transfers. The Rights Agreement, as amended in 2015 (the “Amended Rights Agreement”) limits the maximum amount of penalties and/or exit fee (the “Rusnano Payment”) to be paid by the Company to $5.0 million in the aggregate and allows such payment to be reduced when certain milestones are met over time. The Amended Rights Agreement also provides for an updated investment plan for the Company’s Russian subsidiaries that includes non-cash transfer of licensing rights to intellectual property, non-cash transfers of existing equipment and commitments to complete the remaining investment milestones through 2019. The Company fulfilled its investment commitment required by 2016 and had contributed over $21.0 million in cash and assets to its subsidiaries in Russia as of December 31, 2016. As of September 30, 2018, the remaining Investment Commitment was approximately $7.5 million to be invested at any time on or before December 31, 2019. At any point between September 30, 2018 and December 31, 2019, the Company may elect to pay a $2.0 million exit fee to terminate any remaining obligations associated with the Investment Commitment. In August 2016, the Company entered into a letter of agreement with Rusnano to agree to transfer a 10G SFP+ transceiver product line and incur expected costs of approximately $0.1 million , by July 30, 2017, which will not be counted toward the Company’s overall Investment Commitment. Since the asset sale of the Company’s Low Speed Transceiver Products was completed in January 2017, the Company may undertake an alternative path for spending such amount to be discussed and agreed between the parties. Rusnano has non-transferable veto rights over the Company’s Russian subsidiaries’ annual budget during the investment period and must approve non-cash asset transfers to be made in satisfaction of the Investment Commitment. The Company accounted for the Rusnano Payment as an embedded derivative instrument. The fair value of the Penalty Payment derivative has been estimated at the date of the original common stock sale (April 27, 2012) and at each subsequent balance sheet date using a probability-weighted discounted future cash flow approach using unobservable inputs, which are classified as Level 3 within the fair value hierarchy. The primary inputs for this approach include the probability of achieving the Investment Commitment and a discount rate that approximates the Company’s incremental borrowing rate. After the initial measurement, changes in the fair value of this derivative are recorded in other income (expense), net. The estimated fair value of this derivative was $2.0 million as of September 30, 2018 and $0.4 million as of December 31, 2017 . As of September 30, 2018 , and December 31, 2017, the derivative was reported within Accrued and other current liabilities and other noncurrent liabilities, respectively on the Company’s condensed consolidated balance sheets. See Note 7.

Stockholders' equity

Stockholders' equity	9 Months Ended
	Sep. 30, 2018
Stockholders' Equity Note [Abstract]
Stockholders’ equity	Stockholders’ equity Common Stock As of September 30, 2018 , the Company had reserved 7,857,810 common stock for issuance under its equity incentive plans and 644,187 common stock shares for issuance under its employee stock purchase plan. Accumulated Other Comprehensive Income (loss) The components of accumulated other comprehensive income (loss), net of related taxes, were as follows (in thousands): Foreign Currency Translation Adjustments Unrealized Gain (Loss) on Available-For-Sale Securities Defined Benefit Pension Plan Adjustment Total Accumulated Other Comprehensive Income (loss) Balance as of December 31, 2017 $ 567 $ (1 ) $ (168 ) $ 398 Other comprehensive income (loss), net of taxes of zero and reclassifications (7,968 ) 1 — (7,967 ) Balance as of September 30, 2018 $ (7,401 ) $ — $ (168 ) $ (7,569 ) No material amounts were reclassified out of accumulated other comprehensive income during the three and nine months ended September 30, 2018 and 2017 for realized gains or losses on available-for-sale securities. Accumulated Deficit Approximately $8.8 million of the Company’s retained earnings within its total accumulated deficit as of December 31, 2017 was subject to restriction due to the fact that the Company’s subsidiaries in China are required to set aside at least 10% of their respective accumulated profits each year end to fund statutory common reserves as well as allocate a discretional portion of their after-tax profits to their staff welfare and bonus fund.

Stock-based compensation

Stock-based compensation	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based compensation	Stock-based compensation The following table summarizes the stock-based compensation expense recognized in the three and nine months ended September 30, 2018 and 2017 (in thousands): Three Months Ended Nine Months Ended 2018 2017 2018 2017 Cost of goods sold $ 553 $ 340 $ 1,832 $ 811 Research and development 1,016 606 2,618 1,779 Sales and marketing 931 393 2,511 1,170 General and administrative 1,541 595 3,566 1,932 $ 4,041 $ 1,934 $ 10,527 $ 5,692 Determining Fair Value The Company estimated the fair value of certain stock-based awards using a Black-Scholes-Merton valuation model with the following assumptions: Three Months Ended Nine Months Ended Stock options 2018 2017 2018 2017 Weighted-average expected term (years) 0.00 6.00 6.02 6.00 Weighted-average volatility —% 65% 65% 65% Risk-free interest rate —% 2.02% 2.27%-2.62% 2.02%-2.08% Expected dividends —% —% —% —% Stock appreciation units Weighted-average expected term (years) 1.87 2.20 1.99 2.30 Weighted-average volatility 65% 71% 66% 71% Risk-free interest rate 1.73%-2.52% 1.03%-1.55% 1.03%-2.52% 0.51%-1.55% Expected dividends —% —% —% —% ESPP Weighted-average expected term (years) 0.00 0.00 0.71 0.67 Weighted-average volatility —% —% 61% 55% Risk-free interest rate —% —% 1.20%-1.93% 0.45%-0.91% Expected dividends —% —% —% —% Stock Options and Restricted Stock Units (RSUs) The following table summarizes the Company’s stock option and RSU activity, excluding market-based RSUs, during the nine months ended September 30, 2018: Stock Options Restricted Stock Units Number of Shares Weighted Average Exercise Price Number of Units Weighted Average Grant Date Fair Value Balance as of December 31, 2017 3,933,529 $ 5.55 2,404,637 $ 9.02 Granted 158,116 6.64 1,355,262 6.80 Exercised/Converted (591,322 ) 4.33 (915,713 ) 9.02 Cancelled/Forfeited (95,251 ) 10.24 (214,048 ) 8.80 Balance as of September 30, 2018 3,405,072 5.68 2,630,138 7.89 Market-based Restricted Stock Units In July 2018, the Company granted 665,000 shares of market-based RSUs to certain employees. These RSUs will vest if the 30-day weighted average closing price of the Company's common stock is equal to or greater than certain price targets per share and the recipients remain in continuous service with the Company through such service period. No market-based RSUs were vested/cancelled during 2018. The weighted average grant-date fair value per share of market-based RSUs granted during 2018 was approximately $5.82 per share. The fair value of market-based RSUs was measured on the grant date using Monte Carlo simulation model with the following assumptions: Three Months Ended Nine Months Ended Market-based restricted stock units 2018 2017 2018 2017 Weighted-average volatility 66% —% 66% —% Risk-free interest rate 2.79% —% 2.79% —% Expected dividends —% —% —% —% Stock Appreciation Units (SAU) SAUs are liability classified share-based awards. Outstanding SAUs are re-measured each reporting period at fair value until settlement. The Company did not grant any SAUs during the three and nine months ended September 30, 2018 or 2017 . As of September 30, 2018 and December 31, 2017 , there were 213,205 and 239,824 SAUs outstanding, respectively, and related SAU liabilities were $1.0 million and $0.8 million , respectively. Employee Stock Purchase Plan (ESPP) As of September 30, 2018 , there was $0.1 million of unrecognized stock-based compensation expense for employee stock purchase rights that will be recognized over the remaining offering period through November 2018.

Income taxes

Income taxes	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income taxes	Income taxes The income tax (provision) benefit for income taxes in the periods presented is based upon the income (loss) before income taxes (in thousands): Three Months Ended Nine Months Ended 2018 2017 2018 2017 Income tax (provision) benefit $ (291 ) $ 1,195 $ (2,009 ) $ 1,813 The Company’s income tax (provision) benefit in the three and nine months ended September 30, 2018 and 2017 was primarily related to income taxes of the Company’s non-U.S. operations. The Company conducts its business globally and its operating income is subject to varying rates of tax in the U.S., China and Japan. Consequently, the Company’s effective tax rate is dependent upon the geographic distribution of its earnings or losses and the tax laws and regulations in each geographical region. Historically, the Company has experienced net losses in the U.S. and in the short term, expects this trend to continue. Due to historical losses in the U.S., the Company has a full valuation allowance on its U.S. federal and state deferred tax assets. Management continues to evaluate the realizability of deferred tax assets and the related valuation allowance. If management's assessment of the deferred tax assets or the corresponding valuation allowance were to change, the Company would record the related adjustment to income during the period in which management makes the determination. On December 22, 2017, the U.S. President signed into U.S. law the Tax Cuts and Jobs Act of 2017 ("Tax Reform"). The new legislation, among other provisions, lowered the corporate tax rate from 35% to 21%. The SEC staff issued Staff Accounting Bulletin 118 (“SAB 118”) which provides guidance on accounting for the tax effects of the Tax Reform. SAB 118 provides a measurement period that should not extend beyond one year from the Tax Reform enactment date for companies to complete the accounting under ASC 740, Income Taxes. In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the Tax Reform for which the accounting under ASC 740 is complete. To the extent that a company’s accounting for certain income tax effects of the Tax Reform is incomplete but it is able to determine a reasonable estimate, it must record a provisional estimate in the financial statements. If a company cannot determine a provisional estimate to be included in the financial statements, it should continue to apply ASC 740 on the basis of the provisions of the tax laws that were in effect immediately before the enactment of the Tax Reform. The Company expects to complete its analysis within the measurement period in accordance with SAB 118. The Company adopted ASU 2016-16 on a modified retrospective basis effective January 1, 2018. Upon adoption of this standard on January 1, 2018, the Company recorded $1.8 million to accumulated deficit balance for intra-entity transfer of an asset other than inventory in prior years. As of September 30, 2018 , there were no material changes to either the nature or the amounts of the uncertain tax positions previously determined for the year ended December 31, 2017 .

Subsequent events

Subsequent events	9 Months Ended
	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent events	Subsequent events In October 2018, the Company repaid $5.0 million to Wells Fargo

Basis of presentation and sig_2

Basis of presentation and significant accounting policies (Policies)	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The condensed consolidated financial statements of NeoPhotonics Corporation (“NeoPhotonics” or the “Company”) as of September 30, 2018 and for the three and nine months ended September 30, 2018 and 2017 , have been prepared in accordance with the instructions on Form 10-Q pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). In accordance with those rules and regulations, the Company has omitted certain information and notes normally provided in the Company’s annual consolidated financial statements. In the opinion of management, the condensed consolidated financial statements contain all adjustments, consisting only of normal recurring items, except as otherwise noted, necessary for the fair presentation of the Company’s financial position and results of operations for the interim periods. The year-end condensed consolidated balance sheet data was derived from audited financial statements, but does not include all disclosures required by U.S. generally accepted accounting principles (“U.S. GAAP”). These condensed consolidated financial statements should be read in conjunction with the Consolidated Financial Statements and Notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2017 . The results of operations for the three and nine months ended September 30, 2018 are not necessarily indicative of the results expected for the entire fiscal year. All intercompany accounts and transactions have been eliminated.
Going Concern	Going Concern Accounting Standards Update (“ASU”) No. 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern , requires an entity to disclose information about its potential inability to continue as a going concern when conditions and events indicate that it is probable that the entity may be unable to meet its obligations as they become due within one year. Management has assessed the Company’s ability to continue as a going concern within one year of the filing date of this Quarterly Report on Form 10-Q with the SEC in November 2018. The accompanying unaudited condensed financial statements have been prepared assuming that the Company will continue as a going concern, which contemplates the realization of assets and satisfaction of liabilities in the normal course of business.
Certain Significant Risks And Uncertainties	Certain Significant Risks and Uncertainties The Company operates in a dynamic industry and, accordingly, can be affected by a variety of factors. For example, any of the following areas could have a negative effect on the Company in terms of its future financial position, results of operations or cash flows: the general state of the U.S., China and world economies; the highly cyclical nature of the industries the Company serves; the loss of any of a small number of its larger customers; ability to obtain additional financing; inability to meet certain debt covenants; fundamental changes in the technology underlying the Company’s products; the hiring, training and retention of key employees; successful and timely completion of product design efforts; and new product design introductions by competitors.
Use of Estimates	Use of Estimates The preparation of financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported revenue and expenses during the reporting period. Significant estimates made by management include: the useful lives of property, plant and equipment and intangible assets as well as future cash flows to be generated by those assets; fair values of identifiable assets acquired and liabilities assumed in business combinations; allowances for doubtful accounts; valuation allowances for deferred tax assets; valuation of excess and obsolete inventories; warranty reserves; litigation accrual and recognition of stock-based compensation, among others. Actual results could differ from these estimates.
Accounting Standards Update Recently Adopted/Recent Accounting Standards Update Not Yet Effective	Accounting Standards Update Recently Adopted In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2014-9, Revenue from Contracts with Customers (“ASU 2014-9”). The standard, along with the amendments issued in 2016 and 2015, provides companies with a single model for use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific revenue guidance. The core principle of the model is to recognize revenue when control of the goods or services transfers to the customer, as opposed to recognizing revenue when the risks and rewards transfer to the customer under the existing revenue guidance. ASU 2014-9 is required to be adopted, using either of two methods: (i) retrospective to each prior reporting period presented with the option to elect certain practical expedients as defined within ASU 2014-9; or (ii) retrospective with the cumulative effect of initially applying ASU 2014-9 recognized at the date of initial application and providing certain additional disclosures. This standard, as amended, is effective for annual and interim periods beginning after December 15, 2017 and permits entities to early adopt for annual and interim reporting periods beginning after December 15, 2016. The Company adopted this standard as of January 1, 2018, using the full retrospective transition method. See Note 2 for further details. In May 2017, the FASB issued ASU No. 2017-9, Compensation—Stock Compensation (718)—Scope of Modification Accounting (ASU 2017-9”). This guidance redefines which changes to the terms and conditions of a share-based payment award require an entity to apply modification accounting for a share-based payment. ASU 2017-9 is effective for interim and annual periods after December 15, 2017 and early adoption is permitted in any interim period. The Company adopted this standard effective January 1, 2018. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. In January 2017, the FASB issued ASU 2017-1, Business Combinations (Topic 805): Clarifying the Definition of a Business (“ASU 2017-1”). This standard provides a framework in determining when a set of assets and activities is a business. ASU 2017-1 is effective for interim and annual periods beginning after December 15, 2017 on a prospective basis. The Company adopted this standard effective January 1, 2018. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (“ASC 2016-18”). This standard provides guidance on the classification and presentation of restricted cash in the statement of cash flows and must be applied retrospectively. ASU 2016-18 is effective for fiscal years beginning after December 15, 2017. The Company adopted this standard effective January 1, 2018. The reclassified restricted cash balances from investing activities to changes in cash, cash equivalents and restricted cash on the condensed consolidated statements of cash flows were not material for all periods presented. In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory (“ASU 2016-16”). This standard provides guidance on the tax accounting for the transferring and receiving entities upon transfer of an asset. ASU 2016-16 is effective for the Company’s interim and annual periods beginning after December 15, 2017 and should be applied on a modified retrospective basis. Upon adoption of this standard on January 1, 2018, the Company recorded $1.8 million to accumulated deficit balance for intra-entity transfer of an asset other than inventory in prior years. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”). This standard provides guidance on the classification of certain cash receipts and payments in the statement of cash flows. It is effective, retrospectively, for the Company’s annual and interim reporting periods beginning after December 15, 2017 or prospectively from the earliest date practicable if retrospective application is impracticable. The Company adopted this standard effective January 1, 2018, using the retrospective transition method. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. In January 2016, the FASB issued ASU 2016-1, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities (“ASU 2016-1”). ASU 2016-1 revises an entity’s accounting related to (1) the classification and measurement of investments in equity securities and (2) the presentation of certain fair value changes for financial liabilities measured at fair value. It also amends certain disclosure requirements associated with the fair value of financial instruments and is effective for the Company’s annual and interim reporting periods beginning after December 15, 2017. The Company adopted this standard effective January 1, 2018. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. In March 2017, the FASB issued ASU No. 2017-7, Compensation-Retirement Benefits (Topic 715)-Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost (“ASU 2017-7”). This guidance revises the presentation of employer-sponsored defined benefit pension and other postretirement plans for the net periodic benefit cost in the statement of operations and requires that the service cost component of net periodic benefit be presented in the same income statement line items as other employee compensation costs for services rendered during the period. The other components of the net benefit costs are required to be presented in the statement of operations separately from the service cost component and outside the subtotal of income from operations. This guidance allows only the service cost component of net periodic benefit costs to be eligible for capitalization. ASU 2017-7 is effective for interim and annual periods after December 15, 2017. The Company adopted this standard effective January 1, 2018. The impact on the Company's consolidated financial statements upon the adoption of this standard was immaterial. There have been no other changes in the Company’s significant accounting policies in the nine months ended September 30, 2018, as compared to the significant accounting policies described in its Annual Report on Form 10-K for the year ended December 31, 2017 . Recent Accounting Standards Update Not Yet Effective In January 2017, the FASB issued ASU 2017-4, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (“ASU 2017-4”). This standard amends the goodwill impairment test to compare the fair value of a reporting unit with its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value, up to the total amount of goodwill allocated to that reporting unit. ASU 2017-4 is effective prospectively for interim and annual periods beginning after December 15, 2019. Early adoption is permitted for interim and annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company has not determined whether it will elect early adoption and is currently evaluating the impact of the adoption of this standard on its consolidated financial statements and related disclosures. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 amends existing guidance on the impairment of financial assets and adds an impairment model that is based on expected losses rather than incurred losses and requires an entity to recognize as an allowance its estimate of expected credit losses for its financial assets. An entity will apply this guidance through a cumulative-effect adjustment to retained earnings upon adoption (a modified-retrospective approach) while a prospective transition approach is required for debt securities for which an other-than-temporary impairment had been recognized before the effective date. It is effective for the Company’s annual and interim reporting periods beginning after December 15, 2019. Early adoption is permitted. The Company is in the process of evaluating the impact of the adoption on its consolidated financial statements and related disclosure. In February 2016, the FASB issued ASU 2016-2, Leases (Topic 842) (“ASU 2016-2”). ASU 2016-2 introduces a lessee model that requires recognition of assets and liabilities arising from qualified leases on the consolidated balance sheets and consolidated statements of operations and to disclose qualitative and quantitative information about lease transactions. It is effective for interim and annual periods beginning after December 15, 2018. Early adoption is permitted. Certain optional practical expedients are allowed. The Company is in the process of evaluating the impact of the adoption on its consolidated financial statements and related disclosure.

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Summary of Revenue by Product Group and Geographical Region	The following presents revenue by product group (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 High Speed Products $ 68,519 $ 59,426 $ 197,362 $ 177,488 Network Products and Solutions 13,229 11,695 34,074 38,535 Total revenue $ 81,748 $ 71,121 $ 231,436 $ 216,023 The following table presents the Company's revenue information by geographical region. Revenue is classified based on the ship to location requested by the customer. Such classification recognizes that for many customers, including those in North America or in Europe, designated shipping points are often in China or elsewhere in Asia (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 China $ 46,134 $ 40,513 $ 133,917 $ 117,599 Americas 22,369 13,487 52,270 36,853 Rest of world 13,245 17,121 45,249 61,571 Total revenue $ 81,748 $ 71,121 $ 231,436 $ 216,023

Net loss per share (Tables)

Net loss per share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Income per Share	The following table sets forth the computation of the basic and diluted net loss per share for the periods indicated (in thousands, except per share amounts): Three Months Ended Nine Months Ended 2018 2017 2018 2017 Numerator: Net loss $ (8,125 ) $ (18,187 ) $ (36,908 ) $ (39,050 ) Denominator: Weighted average shares used to compute per share amount: Basic 45,476 43,790 44,804 43,212 Diluted 45,476 43,790 44,804 43,212 Basic net loss per share $ (0.18 ) $ (0.42 ) $ (0.82 ) $ (0.90 ) Diluted net loss per share $ (0.18 ) $ (0.42 ) $ (0.82 ) $ (0.90 )
Potentially Dilutive Securities Excluded from Computation of Diluted Net Income per Share Attributable to Common Stockholders	The Company has excluded the impact of the following outstanding employee stock options and restricted stock units as well as the shares expected to be issued under its employee stock purchase plan from the computation of diluted net loss per share, as their effect would have been antidilutive (in thousands): September 30, 2018 September 30, 2017 Employee stock options 3,405 4,227 Restricted stock units 2,630 2,504 Market-based restricted stock units 665 — Employee stock purchase plan 174 245 6,874 6,976

Cash, cash equivalents, short_2

Cash, cash equivalents, short-term investments, and restricted cash (Tables)	9 Months Ended
	Sep. 30, 2018
Cash and Cash Equivalents [Abstract]
Summary of Cash, Cash Equivalents and Short-Term investments and Restricted Cash and Investments	The following table summarizes the Company’s cash, cash equivalents, short-term investments and restricted cash (in thousands): September 30, December 31, Cash and cash equivalents: Cash $ 52,099 $ 78,906 Cash equivalents — — Cash and cash equivalents $ 52,099 $ 78,906 Short-term investments $ 7,441 $ 12,311 Restricted cash $ 5,195 $ 2,658 September 30, December 31, Cash and cash equivalents $ 52,099 $ 78,906 Restricted cash 5,195 2,658 Total cash, cash equivalents and restricted cash shown in the statement of cash flows $ 57,294 $ 81,564
Summary of Unrealized Gains and Losses Related to Cash Equivalents and Investments in Marketable Securities	The following table summarizes the Company’s unrealized gains and losses related to its cash equivalents and short-term investments in marketable securities designated as available-for-sale (in thousands): As of September 30, 2018 As of December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Loss Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Loss Fair Value Marketable securities: Money market funds $ 7,441 $ — $ — $ 7,441 $ 11,561 $ — $ — $ 11,561 U.S. government securities — — — — 751 — (1 ) 750 Total $ 7,441 $ — $ — $ 7,441 $ 12,312 $ — $ (1 ) $ 12,311 Reported as: Short-term investments 7,441 — — 7,441 12,312 — (1 ) 12,311 Total $ 7,441 $ — $ — $ 7,441 $ 12,312 $ — $ (1 ) $ 12,311
Maturities of Marketable Securities	As of September 30, 2018 and December 31, 2017 , maturities of marketable securities were as follows (in thousands): September 30, December 31, Less than 1 year $ 7,441 $ 12,311 Due in 1 to 2 years — — Due in 3 to 5 years — — Total $ 7,441 $ 12,311

Fair value disclosures (Tables)

Fair value disclosures (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets	The following table presents the Company's assets that are measured at fair value on a recurring basis (in thousands): As of September 30, 2018 As of December 31, 2017 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Cash equivalents and short-term investments: Money market funds $ 7,441 $ — $ — $ 7,441 $ 11,561 $ — $ — $ 11,561 U.S. government securities — — — — 750 — — 750 Total $ 7,441 $ — $ — $ 7,441 $ 12,311 $ — $ — $ 12,311 Foreign currency forward contracts* $ — $ — $ — $ — $ — $ — $ — $ — Mutual funds held in Rabbi Trust, recorded in other long-term assets $ 569 $ — $ — $ 569 $ 523 $ — $ — $ 523 ________________________________________________________ *The fair value of the Company’s foreign currency forward contract was immaterial as of December 31, 2017.
Fair Value of Financial Liabilities	The following table presents the Company's liabilities that are measured at fair value on a recurring basis (in thousands): As of September 30, 2018 As of December 31, 2017 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Rusnano payment derivative $ — $ — $ 2,000 $ 2,000 $ — $ — $ 389 $ 389 Foreign currency forward contracts — — — — — 43 — 43 $ — $ — $ 2,000 $ 2,000 $ — $ 43 $ 389 $ 432

Balance sheet components (Table

Balance sheet components (Tables)	9 Months Ended
	Sep. 30, 2018
Balance Sheet Related Disclosures [Abstract]
Accounts receivable, Net	Accounts receivable, net, consists of the following (in thousands): September 30, 2018 December 31, 2017 Accounts receivable $ 66,264 $ 65,499 Trade notes receivable 476 2,356 Allowance for doubtful accounts (120 ) (626 ) $ 66,620 $ 67,229
Inventories, net	Inventories, net consist of the following (in thousands): September 30, 2018 December 31, 2017 Raw materials $ 26,904 $ 33,400 Work in process 11,755 13,246 Finished goods (1) 18,465 20,655 $ 57,124 $ 67,301 ________________________________________________________ (1) Finished goods inventory at customer vendor managed inventory locations was $6.8 million and $7.1 million as of September 30, 2018 and December 31, 2017 , respectively.
Prepaid expenses and other current assets	Prepaid expenses and other current assets consist of the following (in thousands): September 30, 2018 December 31, 2017 Prepaid taxes and taxes receivable $ 7,167 $ 15,162 Transition services agreement receivable (Note 6) 12,120 12,817 Deposits and other prepaid expenses 3,975 4,138 Other receivable 5,397 4,118 $ 28,659 $ 36,235
Purchased intangible assets	Purchased intangible assets consist of the following (in thousands): September 30, 2018 December 31, 2017 Gross Assets Accumulated Amortization Net Assets Gross Accumulated Net Technology and patents $ 37,045 $ (34,833 ) $ 2,212 $ 37,684 $ (34,923 ) $ 2,761 Customer relationships 15,123 (14,888 ) 235 15,425 (14,835 ) 590 Leasehold interest 1,240 (367 ) 873 1,309 (366 ) 943 $ 53,408 $ (50,088 ) $ 3,320 $ 54,418 $ (50,124 ) $ 4,294
Amortization expense of purchased intangible assets	The following table presents details of the amortization expense of the Company’s purchased intangible assets as reported in the condensed consolidated statements of operations (in thousands): Three Months Ended Nine Months Ended 2018 2017 2018 2017 Cost of goods sold $ 185 $ 202 $ 572 $ 667 Operating expenses 118 119 357 355 Total $ 303 $ 321 $ 929 $ 1,022
Estimated future amortization expense of purchased intangible assets	The estimated future amortization expense of purchased intangible assets as of September 30, 2018 , is as follows (in thousands): 2018 (remaining three months) $ 302 2019 855 2020 737 2021 645 2022 28 Thereafter 753 $ 3,320
Accrued and other current liabilities	Accrued and other current liabilities consist of the following (in thousands): September 30, 2018 December 31, 2017 Transition services agreement payables (Note 6) $ 11,769 $ 11,222 Employee-related 14,742 12,990 Asset sale related contingent liabilities (Note 6) 6,760 7,135 Accrued warranty 1,199 1,334 Deferred revenue, current 704 939 Income and other taxes payable 2,376 542 Rusnano payment derivative 2,000 — Other accrued expenses 7,307 9,080 $ 46,857 $ 43,242
Warranty accrual	The table below summarizes the movement in the warranty accrual, which is included in accrued and other current liabilities (in thousands): Three Months Ended Nine Months Ended 2018 2017 2018 2017 Beginning balance $ 1,592 $ 528 $ 1,334 $ 678 Warranty accruals (42 ) 1,047 487 1,019 Settlements (351 ) (173 ) (622 ) (295 ) Ending balance $ 1,199 $ 1,402 $ 1,199 $ 1,402
Other noncurrent liabilities	Other noncurrent liabilities consist of the following (in thousands): September 30, 2018 December 31, 2017 Pension and other employee-related $ 4,651 $ 4,675 Deferred rent 3,023 2,908 Deferred revenue 112 617 Government grant 1,912 1,095 Rusnano payment derivative — 389 Deferred income tax liabilities 63 106 Asset retirement obligations and other 3,627 4,285 $ 13,388 $ 14,075

Restructuring (Tables)

Restructuring (Tables)	9 Months Ended
	Sep. 30, 2018
Restructuring and Related Activities [Abstract]
Restructuring and Related Costs	Restructuring activities for the nine months ended September 30, 2018 were as follows (in thousands): Employee Severance Facilities Consolidation Others Total Restructuring obligations December 31, 2017 $ — $ 1,580 $ 43 $ 1,623 Charges 269 — 1,704 1,973 Cash payments (147 ) (640 ) (43 ) (830 ) Non-cash settlements and others — — (94 ) (94 ) Restructuring obligations September 30, 2018 $ 122 $ 940 $ 1,610 $ 2,672

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Carrying Amount and Weighted Average Interest Rate of the Company's Debt	The table below summarizes the carrying amount and weighted average interest rate of the Company’s debt (in thousands, except percentages): September 30, 2018 December 31, 2017 Carrying Amount Interest Rate Carrying Interest Note payable to Shanghai Pudong Development Bank $ — $ 17,000 4.10 % Note payable to China CITIC Bank — 17,000 4.00 % Notes payable to suppliers 3,634 — 1,607 Total notes payable and short-term borrowing $ 3,634 $ 35,607 Long-term debt, current and non-current: Borrowing under Wells Fargo Credit Facility $ 35,630 4.51 % $ 30,018 3.29 % Mitsubishi Bank loans 11,206 1.05% -1.45% 16,924 1.05% -1.45% Mitsubishi Bank and Yamanashi Chou Bank loan 6,942 1.1 % — Unaccreted discount and issuance costs within current portion of long-term debt (161 ) (86 ) Unaccreted discount and issuance costs within long-term debt, net of current portion (463 ) (295 ) Total long-term debt, net of unaccreted discount and issuance costs $ 53,154 $ 46,561 Reported as: Current portion of long-term debt $ 2,798 $ 6,005 Long-term debt, net of current portion 50,356 40,556 Total long-term debt, net of unaccreted discount and issuance costs $ 53,154 $ 46,561
Maturities of Long-term Debt	As of September 30, 2018 , maturities of total long-term debt were as follows (in thousands): 2018 (remaining three months) $ 740 2019 2,959 2020 2,959 2021 2,959 2022 38,589 Thereafter 5,572 $ 53,778

Stockholders' equity (Tables)

Stockholders' equity (Tables)	9 Months Ended
	Sep. 30, 2018
Stockholders' Equity Note [Abstract]
Schedule of Accumulated Other Comprehensive Income, Net of Related Taxes	The components of accumulated other comprehensive income (loss), net of related taxes, were as follows (in thousands): Foreign Currency Translation Adjustments Unrealized Gain (Loss) on Available-For-Sale Securities Defined Benefit Pension Plan Adjustment Total Accumulated Other Comprehensive Income (loss) Balance as of December 31, 2017 $ 567 $ (1 ) $ (168 ) $ 398 Other comprehensive income (loss), net of taxes of zero and reclassifications (7,968 ) 1 — (7,967 ) Balance as of September 30, 2018 $ (7,401 ) $ — $ (168 ) $ (7,569 )

Stock-based compensation (Table

Stock-based compensation (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock Based Compensation Expense	The following table summarizes the stock-based compensation expense recognized in the three and nine months ended September 30, 2018 and 2017 (in thousands): Three Months Ended Nine Months Ended 2018 2017 2018 2017 Cost of goods sold $ 553 $ 340 $ 1,832 $ 811 Research and development 1,016 606 2,618 1,779 Sales and marketing 931 393 2,511 1,170 General and administrative 1,541 595 3,566 1,932 $ 4,041 $ 1,934 $ 10,527 $ 5,692
Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions	The Company estimated the fair value of certain stock-based awards using a Black-Scholes-Merton valuation model with the following assumptions: Three Months Ended Nine Months Ended Stock options 2018 2017 2018 2017 Weighted-average expected term (years) 0.00 6.00 6.02 6.00 Weighted-average volatility —% 65% 65% 65% Risk-free interest rate —% 2.02% 2.27%-2.62% 2.02%-2.08% Expected dividends —% —% —% —% Stock appreciation units Weighted-average expected term (years) 1.87 2.20 1.99 2.30 Weighted-average volatility 65% 71% 66% 71% Risk-free interest rate 1.73%-2.52% 1.03%-1.55% 1.03%-2.52% 0.51%-1.55% Expected dividends —% —% —% —% ESPP Weighted-average expected term (years) 0.00 0.00 0.71 0.67 Weighted-average volatility —% —% 61% 55% Risk-free interest rate —% —% 1.20%-1.93% 0.45%-0.91% Expected dividends —% —% —% —%
Estimated Fair Value of Certain Stock-Based Awards Using Black-Scholes-Merton Valuation Model	The fair value of market-based RSUs was measured on the grant date using Monte Carlo simulation model with the following assumptions: Three Months Ended Nine Months Ended Market-based restricted stock units 2018 2017 2018 2017 Weighted-average volatility 66% —% 66% —% Risk-free interest rate 2.79% —% 2.79% —% Expected dividends —% —% —% —%
Summary of Stock Option and Restricted Stock Unit Activity	The following table summarizes the Company’s stock option and RSU activity, excluding market-based RSUs, during the nine months ended September 30, 2018: Stock Options Restricted Stock Units Number of Shares Weighted Average Exercise Price Number of Units Weighted Average Grant Date Fair Value Balance as of December 31, 2017 3,933,529 $ 5.55 2,404,637 $ 9.02 Granted 158,116 6.64 1,355,262 6.80 Exercised/Converted (591,322 ) 4.33 (915,713 ) 9.02 Cancelled/Forfeited (95,251 ) 10.24 (214,048 ) 8.80 Balance as of September 30, 2018 3,405,072 5.68 2,630,138 7.89

Income taxes (Tables)

Income taxes (Tables)	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Summary of Income Tax (Provisions) Benefits	The income tax (provision) benefit for income taxes in the periods presented is based upon the income (loss) before income taxes (in thousands): Three Months Ended Nine Months Ended 2018 2017 2018 2017 Income tax (provision) benefit $ (291 ) $ 1,195 $ (2,009 ) $ 1,813

Basis of presentation and sig_3

Basis of presentation and significant accounting policies - (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Jan. 01, 2018
Concentration Risk [Line Items]
Working capital	$ 112,400,000		$ 112,400,000
Cash, cash equivalents, short-term investments and restricted cash	64,700,000		64,700,000
Operating losses	(8,689,000)	$ (18,883,000)	(35,083,000)	$ (40,458,000)
Net cash from operating activities			8,997,000	$ (41,211,000)
Accumulated deficit	390,743,000		390,743,000		$ 352,011,000
Notes payable and short-term borrowing	3,634,000		3,634,000		35,607,000
Current portion of long-term debt	$ 2,798,000		$ 2,798,000		$ 6,005,000
Huawei Technologies | Revenue
Concentration Risk [Line Items]
Percentage of concentration of credit risk	47.00%	39.00%	47.00%	39.00%
Top Five Customers | Revenue
Concentration Risk [Line Items]
Percentage of concentration of credit risk	89.00%	79.00%	89.00%	76.00%
Customer One | Revenue
Concentration Risk [Line Items]
Percentage of concentration of credit risk	28.00%	14.00%	25.00%	16.00%
Customer One | Accounts receivable
Concentration Risk [Line Items]
Percentage of concentration of credit risk			41.00%		36.00%
Customer Two | Revenue
Concentration Risk [Line Items]
Percentage of concentration of credit risk		11.00%
Customer Two | Accounts receivable
Concentration Risk [Line Items]
Percentage of concentration of credit risk			20.00%		14.00%
Customer three | Accounts receivable
Concentration Risk [Line Items]
Percentage of concentration of credit risk			12.00%		10.00%
Wells Fargo Bank, National Association | Revolving Credit Facility
Concentration Risk [Line Items]
Credit facility, maximum borrowing amount		$ 50,000,000		$ 50,000,000
Line of credit facility, outstanding	$ 35,600,000		$ 35,600,000
Wells Fargo Credit Facility | Line of Credit
Concentration Risk [Line Items]
Credit facility, maximum borrowing amount		50,000,000		50,000,000
Line of credit facility, outstanding		$ 30,000,000		$ 30,000,000
Unused part of credit facility	14,400,000		14,400,000
Minimum required unused borrowing capacity	$ 5,000,000		$ 5,000,000
Accounting Standards Update 2016-16
Concentration Risk [Line Items]
Adjustments to accumulated deficit for new accounting pronouncements						$ 1,800,000

Revenue - Revenue by Product Gr

Revenue - Revenue by Product Group (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Total revenue	$ 81,748	$ 71,121	$ 231,436	$ 216,023
High Speed Products
Disaggregation of Revenue [Line Items]
Total revenue	68,519	59,426	197,362	177,488
Network Products and Solutions
Disaggregation of Revenue [Line Items]
Total revenue	$ 13,229	$ 11,695	$ 34,074	$ 38,535

Revenue - Revenue From External

Revenue - Revenue From External Customers By Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Total revenue	$ 81,748	$ 71,121	$ 231,436	$ 216,023
China
Disaggregation of Revenue [Line Items]
Total revenue	46,134	40,513	133,917	117,599
Americas
Disaggregation of Revenue [Line Items]
Total revenue	22,369	13,487	52,270	36,853
Rest of world
Disaggregation of Revenue [Line Items]
Total revenue	$ 13,245	$ 17,121	$ 45,249	$ 61,571

Revenue - Narrative (Details)

Revenue - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue from Contract with Customer [Abstract]
Contract with customer, liability, revenue recognized	$ 0.2	$ 0.2	$ 0.8	$ 0.7
Increase (decrease) in deferred revenue		$ 0.1		$ 1.7

Net loss per share - Computatio

Net loss per share - Computation of Basic and Diluted Net Income (Loss) per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Numerator:
Net loss	$ (8,125)	$ (18,187)	$ (36,908)	$ (39,050)
Weighted average shares used to compute per share amount:
Basic (in shares)	45,476	43,790	44,804	43,212
Diluted (in shares)	45,476	43,790	44,804	43,212
Basic net loss per share (USD per share)	$ (0.18)	$ (0.42)	$ (0.82)	$ (0.90)
Diluted net loss per share (USD per share)	$ (0.18)	$ (0.42)	$ (0.82)	$ (0.90)

Net loss per share - Potentiall

Net loss per share - Potentially Dilutive Securities Excluded From Computation of Diluted Net Loss per Share Attributable to Common Stockholders (Details) - shares shares in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share (in shares)	6,874	6,976
Employee stock options
Antidilutive Securities Excluded From Computation Of Earnings Per Share
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share (in shares)	3,405	4,227
Restricted stock units
Antidilutive Securities Excluded From Computation Of Earnings Per Share
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share (in shares)	2,630	2,504
Market-based restricted stock units
Antidilutive Securities Excluded From Computation Of Earnings Per Share
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share (in shares)	665	0
Employee stock purchase plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share (in shares)	174	245

Cash, cash equivalents, short_3

Cash, cash equivalents, short-term investments and restricted cash - Short term investments and restricted cash and investments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Cash and cash equivalents:
Cash	$ 52,099	$ 78,906
Cash equivalents	0	0
Cash and cash equivalents	52,099	78,906
Short-term investments	7,441	12,311
Restricted cash	5,195	2,658
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 57,294	$ 81,564	$ 61,445	$ 86,585

Cash, cash equivalents, short_4

Cash, cash equivalents, short-term investments, and restricted cash - Narrative (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)investment	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)investment	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	$ 5,195,000		$ 5,195,000		$ 2,658,000
Restricted cash and investment, government grants, current	1,200,000		1,200,000
Restricted cash and investments, compensating notes payable balance, current	1,900,000		1,900,000
Impairment losses on marketable securities	$ 0	$ 0	$ 0	$ 0
Number of marketable securities in an unrealized loss position | investment	0		0
Disposal Group, Disposed of by Sale, Not Discontinued Operations
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	$ 2,100,000		$ 2,100,000		$ 2,100,000

Cash, cash equivalents, short_5

Cash, cash equivalents, short-term investments and restricted cash - Summary of unrealized gains and losses (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 7,441	$ 12,312
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	(1)
Fair Value	7,441	12,311
Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	7,441	11,561
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	0
Fair Value	7,441	11,561
U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	0	751
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	(1)
Fair Value	0	750
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	7,441	12,312
Gross Unrealized Gains	0	0
Gross Unrealized Loss	0	(1)
Fair Value	$ 7,441	$ 12,311

Cash, cash equivalents, short_6

Cash, cash equivalents, short-term investments and restricted cash - Maturities of marketable securities and additional information (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Less than 1 year	$ 7,441	$ 12,311
Due in 1 to 2 years	0	0
Due in 3 to 5 years	0	0
Total	$ 7,441	$ 12,311

Fair value disclosures - Assets

Fair value disclosures - Assets and liabilities measured at fair value on recurring basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and short-term investments	$ 7,441	$ 12,311
Foreign currency forward contracts	0	0
Rusnano payment derivative	2,000	389
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and short-term investments	7,441	12,311
Foreign currency forward contracts	0	0
Rusnano payment derivative	0	0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and short-term investments	0	0
Foreign currency forward contracts	0	0
Rusnano payment derivative	0	0
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and short-term investments	0	0
Foreign currency forward contracts	0	0
Rusnano payment derivative	2,000	389
Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and short-term investments	7,441	11,561
Money market funds | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and short-term investments	7,441	11,561
Money market funds | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and short-term investments	0	0
Money market funds | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and short-term investments	0	0
U.S. government securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and short-term investments	0	750
U.S. government securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and short-term investments	0	750
U.S. government securities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and short-term investments	0	0
U.S. government securities | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and short-term investments	0	0
Mutual funds held in Rabbi Trust, recorded in other long-term assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mutual funds held in Rabbi Trust, recorded in other long-term assets	569	523
Mutual funds held in Rabbi Trust, recorded in other long-term assets | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mutual funds held in Rabbi Trust, recorded in other long-term assets	569	523
Mutual funds held in Rabbi Trust, recorded in other long-term assets | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mutual funds held in Rabbi Trust, recorded in other long-term assets	0	0
Mutual funds held in Rabbi Trust, recorded in other long-term assets | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mutual funds held in Rabbi Trust, recorded in other long-term assets	0	0
Foreign Exchange Forward
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net asset (liability)	0	43
Foreign Exchange Forward | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net asset (liability)	0	0
Foreign Exchange Forward | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net asset (liability)	0	43
Foreign Exchange Forward | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net asset (liability)	0	0
Derivative
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net asset (liability)	2,000	432
Derivative | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net asset (liability)	0	0
Derivative | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net asset (liability)	0	43
Derivative | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net asset (liability)	$ 2,000	$ 389

Fair value disclosures - Hedgin

Fair value disclosures - Hedging Program (Details)	9 Months Ended
	Sep. 30, 2018
Foreign exchange contracts
Average maturities of monthly foreign exchange contracts	1 month

Fair value disclosures - Liabil

Fair value disclosures - Liabilities measured at fair value on non-recurring basis (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017	Mar. 31, 2017
Other current liabilities | Indemnification agreement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Contingent liability in connection with contingent indemnification commitments	$ 6,800,000
Fair Value, Measurements, Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value, net asset (liability)	$ 0	$ 0
Level 3 | Fair Value, Measurements, Nonrecurring | Other current liabilities | Indemnification agreement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Contingent liability in connection with contingent indemnification commitments			$ 6,700,000

Asset sale (Details)

Asset sale (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Transition services agreement receivable		$ 12,120		$ 12,120		$ 12,817
Transition services agreement payables		11,769		11,769		11,222
Assets held for sale		3,192		3,192		0
Gain within operating income		0	$ 0	0	$ 2,000	2,200
Other current liabilities | Indemnification agreement
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Contingent liability		$ 6,800		$ 6,800
Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale							$ 13,900
Reclassification from assets held-for-sale						3,400
Assets sold						12,800
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Inventories
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale, other							13,100
Assets sold						12,100
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Property, plant and equipment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets held for sale, other							$ 800
Assets sold						700
APAT OE | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration received pursuant to asset purchase agreement	$ 25,000
Proceeds from post-closing transaction services fees under transition services agreement	$ 1,400
Disposal group consideration adjustment						21,600
Consideration adjustment for potential indemnification claims						$ 10,000

Balance sheet components - Acco

Balance sheet components - Accounts receivable, net (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Balance Sheet Related Disclosures [Abstract]
Accounts receivable	$ 66,264	$ 65,499
Trade notes receivable	476	2,356
Allowance for doubtful accounts	(120)	(626)
Account and trade note receivables, net	$ 66,620	$ 67,229

Balance sheet components - Inve

Balance sheet components - Inventories (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Long Lived Assets Held-for-sale [Line Items]
Raw materials	$ 26,904	$ 26,904		$ 26,904		$ 33,400
Work in process	11,755	11,755		11,755		13,246
Finished goods	18,465	18,465		18,465		20,655
Inventories	57,124	57,124		57,124		67,301
Finished goods, at vendor managed inventory locations	6,800	6,800		6,800		7,100
Restructuring charges		1,133	$ 2,829	1,786	$ 3,550
Increase (decrease) in assets held-for-sale				3,200
Assets held for sale	3,192	3,192		3,192		$ 0
Property, plant and equipment
Long Lived Assets Held-for-sale [Line Items]
Assets held for sale	2,600	2,600		2,600
Prepaid Expenses and Other Current Assets
Long Lived Assets Held-for-sale [Line Items]
Assets held for sale	$ 600	600		600
Rusnano Group
Long Lived Assets Held-for-sale [Line Items]
Restructuring charges		$ 1,000		$ 1,600
NeoPhotonics Corporation | Joint Stock Company Rusnano
Long Lived Assets Held-for-sale [Line Items]
Assets held for sale, percent of component acquired	100.00%

Balance sheet components - Prep

Balance sheet components - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Balance Sheet Related Disclosures [Abstract]
Prepaid taxes and taxes receivable	$ 7,167		$ 15,162
Transition services agreement receivable (Note 6)	12,120		12,817
Deposits and other prepaid expenses	3,975		4,138
Other receivable	5,397		4,118
Prepaid expenses and other current assets	28,659		$ 36,235
Capital expenditures incurred but not yet paid	$ 1,100	$ 9,700

Balance sheet components - Purc

Balance sheet components - Purchased intangible assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Assets	$ 53,408	$ 54,418
Accumulated Amortization	(50,088)	(50,124)
Net Assets	3,320	4,294
Technology and patents
Finite-Lived Intangible Assets [Line Items]
Gross Assets	37,045	37,684
Accumulated Amortization	(34,833)	(34,923)
Net Assets	2,212	2,761
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Assets	15,123	15,425
Accumulated Amortization	(14,888)	(14,835)
Net Assets	235	590
Leasehold interest
Finite-Lived Intangible Assets [Line Items]
Gross Assets	1,240	1,309
Accumulated Amortization	(367)	(366)
Net Assets	$ 873	$ 943

Balance sheet components - Amor

Balance sheet components - Amortization expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Balance Sheet Related Disclosures [Abstract]
Cost of goods sold	$ 185	$ 202	$ 572	$ 667
Operating expenses	118	119	357	355
Total	$ 303	$ 321	$ 929	$ 1,022

Balance sheet components - Esti

Balance sheet components - Estimated future amortization expense of purchased intangible assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Balance Sheet Related Disclosures [Abstract]
2018 (remaining three months)	$ 302
2,019	855
2,020	737
2,021	645
2,022	28
Thereafter	753
Net Assets	$ 3,320	$ 4,294

Balance sheet components - Accr

Balance sheet components - Accrued and other current liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Balance Sheet Related Disclosures [Abstract]
Transition services agreement payables (Note 6)	$ 11,769		$ 11,222
Employee-related	14,742		12,990
Asset sale related contingent liabilities (Note 6)	6,760		7,135
Accrued warranty	1,199	$ 1,592	1,334	$ 1,402	$ 528	$ 678
Deferred revenue, current	704		939
Income and other taxes payable	2,376		542
Rusnano payment derivative	2,000		0
Other accrued expenses	7,307		9,080
Accrued and other current liabilities	$ 46,857		$ 43,242

Balance sheet components - Warr

Balance sheet components - Warranty accrual (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Movement in Standard and Extended Product Warranty Accrual, Increase (Decrease) [Roll Forward]
Beginning balance	$ 1,592	$ 528	$ 1,334	$ 678
Warranty accruals	(42)	1,047	487	1,019
Settlements	(351)	(173)	(622)	(295)
Ending balance	$ 1,199	$ 1,402	$ 1,199	$ 1,402

Balance sheet components - Othe

Balance sheet components - Other noncurrent liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Balance Sheet Related Disclosures [Abstract]
Pension and other employee-related	$ 4,651	$ 4,675
Deferred rent	3,023	2,908
Deferred revenue	112	617
Government grant	1,912	1,095
Rusnano payment derivative	0	389
Deferred income tax liabilities	63	106
Asset retirement obligations and other	3,627	4,285
Other noncurrent liabilities	$ 13,388	$ 14,075

Restructuring - Narrative (Deta

Restructuring - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred			$ 1,973
Restructuring reserve recorded in accrued and other current liabilities	$ 2,600		2,600
Restructuring reserve recorded in other noncurrent liabilities	100		100
Cost of goods sold
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred	100		200
Operating Expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred	$ 1,100		$ 1,800
Cost of Sales And Operating Expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges incurred		$ 3,100		$ 4,100

Restructuring - Reserve Rollfor

Restructuring - Reserve Rollforward (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)
Restructuring Reserve [Roll Forward]
Restructuring obligations December 31, 2017	$ 1,623
Charges	1,973
Cash payments	(830)
Non-cash settlements and others	(94)
Restructuring obligations September 30, 2018	2,672
Employee Severance
Restructuring Reserve [Roll Forward]
Restructuring obligations December 31, 2017	0
Charges	269
Cash payments	(147)
Non-cash settlements and others	0
Restructuring obligations September 30, 2018	122
Facilities Consolidation
Restructuring Reserve [Roll Forward]
Restructuring obligations December 31, 2017	1,580
Charges	0
Cash payments	(640)
Non-cash settlements and others	0
Restructuring obligations September 30, 2018	940
Others
Restructuring Reserve [Roll Forward]
Restructuring obligations December 31, 2017	43
Charges	1,704
Cash payments	(43)
Non-cash settlements and others	(94)
Restructuring obligations September 30, 2018	$ 1,610

Debt - Components of Debt Oblig

Debt - Components of Debt Obligations and Weighted Average Interest Rate (Details) $ in Thousands, ¥ in Millions	Sep. 30, 2018USD ($)	Sep. 30, 2018JPY (¥)	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
Short-term debt	$ 3,634		$ 35,607
Unaccreted discount and issuance costs within current portion of long-term debt	(161)		(86)
Unaccreted discount and issuance costs within long-term debt, net of current portion	(463)		(295)
Total long-term debt, net of unaccreted discount and issuance costs	53,154		46,561
Current portion of long-term debt	2,798		6,005
Long-term debt, net of current portion	50,356		40,556
Notes Payable to Banks | Mitsubishi Bank Loans
Debt Instrument [Line Items]
Long-term debt, gross	11,206		16,924
Total long-term debt, net of unaccreted discount and issuance costs | ¥		¥ 641.7
Notes Payable to Banks | Mitsubishi Bank Loans And Yamanashi Chou Bank Loans
Debt Instrument [Line Items]
Long-term debt, gross	$ 6,942
Weighted average interest rate	1.10%	1.10%
Line of Credit | Wells Fargo Credit Facility
Debt Instrument [Line Items]
Long-term debt, gross	$ 35,630		$ 30,018
Weighted average interest rate	4.51%	4.51%	3.29%
Notes Payable to Banks | Note Payable to Shanghai Pudong Development Bank
Debt Instrument [Line Items]
Short-term debt	$ 0		$ 17,000
Weighted average interest rate			4.10%
Notes Payable to Banks | Notes Payable CITIC Bank
Debt Instrument [Line Items]
Short-term debt	$ 0		$ 17,000
Weighted average interest rate			4.00%
Notes payable to suppliers | Loans With Suppliers
Debt Instrument [Line Items]
Short-term debt	$ 3,634		$ 1,607
Minimum | Line of Credit | Mitsubishi Bank Loans
Debt Instrument [Line Items]
Weighted average interest rate			1.05%
Maximum | Line of Credit | Mitsubishi Bank Loans
Debt Instrument [Line Items]
Weighted average interest rate			1.45%

Debt - Notes Payable (Details)

Debt - Notes Payable (Details)	1 Months Ended						9 Months Ended	12 Months Ended
	Aug. 31, 2018USD ($)	May 31, 2018USD ($)	Feb. 28, 2018USD ($)	Jan. 31, 2018USD ($)	Nov. 30, 2017USD ($)	Jul. 31, 2017USD ($)	Sep. 30, 2018CNY (¥)line_of_credit	Dec. 31, 2016USD ($)debt_instrument	Sep. 30, 2018USD ($)line_of_credit	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
Short-term debt									$ 3,634,000	$ 35,607,000
Notes payable to suppliers | Loans With Suppliers
Debt Instrument [Line Items]
Short-term debt									3,634,000	1,607,000
Notes payable to suppliers | Loans With Suppliers | Minimum
Debt Instrument [Line Items]
Debt instrument, term							3 months
Notes payable to suppliers | Loans With Suppliers | Maximum
Debt Instrument [Line Items]
Debt instrument, term							6 months
Loans Payable | First Credit Facility Expires July 2019
Debt Instrument [Line Items]
Current borrowing capacity							¥ 120,000,000		17,500,000
Loans Payable | Second Line Of Credit, Expires July 2019
Debt Instrument [Line Items]
Current borrowing capacity							30,000,000		4,400,000
Bankers Acceptance
Debt Instrument [Line Items]
Restricted cash and investments, current									1,900,000	500,000
Bankers Acceptance | Loans With Suppliers
Debt Instrument [Line Items]
Short-term debt									3,600,000	1,600,000
Bankers Acceptance | First Credit Facility Expires July 2019
Debt Instrument [Line Items]
Current borrowing capacity							¥ 240,000,000		34,900,000
Percentage of compensating balance requirement for bank acceptance drafts							50.00%
Bankers Acceptance | Second Line Of Credit, Expires July 2019
Debt Instrument [Line Items]
Percentage of compensating balance requirement for bank acceptance drafts							50.00%
Short Term Loans | Second Line Of Credit, Expires July 2019
Debt Instrument [Line Items]
Current borrowing capacity							¥ 60,000,000		8,700,000
Notes Payable to Banks | Notes Payable CITIC Bank
Debt Instrument [Line Items]
Proceeds from lines of credit			$ 17,000,000			$ 17,000,000
Debt instrument, interest rate, stated percentage			4.70%
Repayments of lines of credit	$ 17,000,000
Debt instrument, basis spread						2.55%
Short-term debt									$ 0	$ 17,000,000
Letter of Credit
Debt Instrument [Line Items]
Number of debt instruments | debt_instrument								3
Letter of Credit | Loans With Suppliers
Debt Instrument [Line Items]
Percentage of compensating balance requirement for bank acceptance drafts								30.00%
Short-term line of credit facility								$ 1,600,000
China | Notes payable to suppliers | First Credit Facility Expires June Two Thousand Sixteen
Debt Instrument [Line Items]
Proceeds from lines of credit					$ 17,000,000
Repayments of lines of credit		$ 17,000,000
China | Bankers Acceptance | First Credit Facility Expires June Two Thousand Sixteen
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage					4.10%
China | Notes Payable to Banks | Notes Payable CITIC Bank
Debt Instrument [Line Items]
Repayments of lines of credit				$ 17,000,000
Line of Credit | China
Debt Instrument [Line Items]
Number of debt instruments | line_of_credit							3		3
CITIC Bank | Line of Credit | China
Debt Instrument [Line Items]
Credit facility, maximum borrowing amount							¥ 250,000,000		$ 36,400,000
CITIC Bank | Bank Acceptance Drafts | China
Debt Instrument [Line Items]
Percentage of compensating balance requirement for bank acceptance drafts							36.00%
Credit facility, maximum borrowing amount							¥ 390,600,000		$ 56,900,000

Debt - Credit Facilities (Detai

Debt - Credit Facilities (Details) - USD ($)	1 Months Ended		3 Months Ended	9 Months Ended
	Oct. 31, 2018	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Line of Credit Facility [Line Items]
Repayment of notes payable				$ 2,568,000	$ 9,789,000
Capital Expenditures Credit Facility Expires April 30, 2017 | Line of Credit
Line of Credit Facility [Line Items]
Credit facility, maximum borrowing amount							$ 30,000,000
Amended Comerica Bank Credit Facility | Line of Credit
Line of Credit Facility [Line Items]
Current borrowing capacity			$ 17,000,000
Line of credit facility, maximum indebtedness under debt covenant			$ 20,000,000
Credit Facility Base Rate | Amended Comerica Bank Credit Facility | Line of Credit
Line of Credit Facility [Line Items]
Debt instrument, basis spread			1.75%
Libor Plus Rate | Amended Comerica Bank Credit Facility | Line of Credit
Line of Credit Facility [Line Items]
Debt instrument, basis spread			2.75%
Federal funds effective rate | Amended Comerica Bank Credit Facility | Line of Credit
Line of Credit Facility [Line Items]
Debt instrument, basis spread			1.00%
Daily adjusting LIBOR rate | Amended Comerica Bank Credit Facility | Line of Credit
Line of Credit Facility [Line Items]
Debt instrument, basis spread			1.00%
Line of Credit | Wells Fargo Credit Facility
Line of Credit Facility [Line Items]
Credit facility, maximum borrowing amount		$ 50,000,000			50,000,000
Line of credit facility, maximum indebtedness under debt covenant		$ 20,000,000			20,000,000
Cash balance for borrowing		100.00%
Cash balance max borrowing		$ 15,000,000
Line of credit facility increase		25,000,000
Line of credit facility, outstanding		30,000,000			30,000,000
Repayment of notes payable		20,000,000
Unused borrowing capacity		$ 5,000,000			$ 5,000,000
Line of credit fair value outstanding				$ 35,600,000
Weighted average interest rate				4.51%		3.29%
Unused part of credit facility				$ 14,400,000
Minimum required unused borrowing capacity				$ 5,000,000
Line of Credit | Libor Plus Rate | Wells Fargo Credit Facility
Line of Credit Facility [Line Items]
Weighted average interest rate				4.51%
Line of Credit | Prime Rate | Wells Fargo Credit Facility
Line of Credit Facility [Line Items]
Commitment fee		0.25%
Line of Credit | Minimum | Wells Fargo Credit Facility
Line of Credit Facility [Line Items]
Revolver accounts receivable		80.00%
Line of Credit | Minimum | Libor Plus Rate | Wells Fargo Credit Facility
Line of Credit Facility [Line Items]
Debt instrument, basis spread		1.50%
Line of Credit | Minimum | Prime Rate | Wells Fargo Credit Facility
Line of Credit Facility [Line Items]
Debt instrument, basis spread		0.50%
Line of Credit | Maximum | Wells Fargo Credit Facility
Line of Credit Facility [Line Items]
Revolver accounts receivable		85.00%
Line of Credit | Maximum | Libor Plus Rate | Wells Fargo Credit Facility
Line of Credit Facility [Line Items]
Debt instrument, basis spread		1.75%
Line of Credit | Maximum | Prime Rate | Wells Fargo Credit Facility
Line of Credit Facility [Line Items]
Debt instrument, basis spread		0.75%
Subsequent Event | Wells Fargo Credit Facility
Line of Credit Facility [Line Items]
Repayments of lines of credit	$ 5,000,000

Debt - Mitsubishi Bank Loans (D

Debt - Mitsubishi Bank Loans (Details) $ in Thousands	Feb. 25, 2015USD ($)	Feb. 25, 2015JPY (¥)	Jan. 31, 2018USD ($)	Jan. 31, 2018JPY (¥)	Mar. 31, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2018JPY (¥)	Dec. 31, 2017USD ($)	Mar. 31, 2017JPY (¥)	Feb. 25, 2015JPY (¥)
Debt Instrument [Line Items]
Long-term debt | $						$ 53,154		$ 46,561
Notes Payable to Banks | Mitsubishi Bank Term Loan A
Debt Instrument [Line Items]
Debt, aggregate principal amount	$ 4,400									¥ 500,000,000
Notes Payable to Banks | Mitsubishi Bank Term Loan B
Debt Instrument [Line Items]
Debt, aggregate principal amount	$ 8,800									¥ 1,000,000,000
Debt, periodic principal payments		¥ 8,333,000
Debt, lump sum payment on the maturity date		¥ 8,373,000
Long-term debt | $						5,600
Notes Payable to Banks | Mitsubishi Bank Term Loan B | Tokyo interbank offer rate
Debt Instrument [Line Items]
Debt instrument, basis spread	1.40%	1.40%
Notes Payable to Banks | Mitsubishi Bank Loans
Debt Instrument [Line Items]
Loan structuring fee including consumption tax	$ 400	¥ 40,500,000
Long-term debt							¥ 641,700,000
Unamortized debt issuance costs						$ 600	¥ 71,000,000
Notes Payable to Banks | Mitsubishi Bank Loans | Tokyo interbank offer rate
Debt Instrument [Line Items]
Debt instrument, basis spread	1.40%	1.40%
Notes Payable to Banks | 2017 Mitsubishi Bank Loan
Debt Instrument [Line Items]
Debt, aggregate principal amount					$ 6,100				¥ 690,000,000
Debt instrument, term					72 months
Line of credit facility, outstanding					$ 6,100				¥ 690,000,000
Notes Payable to Banks | 2017 Mitsubishi Bank Loan | Tokyo interbank offer rate
Debt Instrument [Line Items]
Debt instrument, basis spread					1.00%
Mitsubishi Bank | Mitsubishi Bank Term Loan A
Debt Instrument [Line Items]
Repayments of lines of credit			$ 4,400	¥ 500,000,000

Debt - Mitsubishi Bank and Yama

Debt - Mitsubishi Bank and Yamanashi Chou Bank Loans (Details) - 1 months ended Jan. 31, 2018 - Mitsubishi Bank and The Yamanashi Chou Bank, Ltd. - Term Loan C $ in Millions	USD ($)	JPY (¥)
Debt Instrument [Line Items]
Credit facility, maximum borrowing amount	$ 7.5	¥ 850,000,000
Debt instrument, term	82 months
Tokyo interbank offer rate
Debt Instrument [Line Items]
Debt instrument, basis spread	1.00%

Debt - Maturities of Long-Term

Debt - Maturities of Long-Term debt (Details) $ in Thousands	Sep. 30, 2018USD ($)
Debt Disclosure [Abstract]
2018 (remaining three months)	$ 740
2,019	2,959
2,020	2,959
2,021	2,959
2,022	38,589
Thereafter	5,572
Total long-term debt, current and non-current	$ 53,778

Japan pension plan - (Details)

Japan pension plan - (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Pension liability	$ 4.1	$ 4.6
Pension liability included in accrued and other current liabilities		$ 0.5

Commitments and Contingencies (

Commitments and Contingencies (Details) ¥ in Thousands, ft² in Thousands

Oct. 25, 2017CNY (¥)

Oct. 25, 2017USD ($)

Jun. 16, 2017USD ($)

Jun. 13, 2017USD ($)ft²

Dec. 27, 2016USD ($)

Sep. 30, 2018USD ($)

Sep. 30, 2016USD ($)ft²

Aug. 31, 2016USD ($)

Sep. 30, 2018USD ($)

Sep. 30, 2017USD ($)

Sep. 30, 2018USD ($)

Sep. 30, 2017USD ($)

Dec. 31, 2016USD ($)

Dec. 31, 2010lawsuitclaim

Dec. 31, 2019USD ($)

Jun. 30, 2018USD ($)

Dec. 31, 2017USD ($)

Dec. 31, 2015USD ($)

Dec. 31, 2012USD ($)

Commitments And Contingencies Disclosure [Line Items]

Number of defendants | lawsuit

4

Operating leases, future minimum payments due

$ 27,800,000

$ 27,800,000

$ 27,800,000

Operating leases, future minimum, sublease receipts

1,400,000

1,400,000

1,400,000

Rent expense

1,100,000

$ 1,300,000

3,200,000

$ 3,500,000

Area of office lease | ft²

39

64

Office lease term, months

123 months

129 months

Office and laboratory lease period free of charge

9 months

Asset retirement obligation

3,100,000

3,100,000

3,100,000

Amount of contribution

$ 21,000,000

Expected costs to transfer product line

$ 100,000

Penalty payment derivative

2,000,000

2,000,000

2,000,000

$ 400,000

Rusnano

Commitments And Contingencies Disclosure [Line Items]

Other non-current liability

$ 0

$ 0

Minimum

Commitments And Contingencies Disclosure [Line Items]

Office lease, monthly rental rate

$ 41,388

$ 144,000

Maximum

Commitments And Contingencies Disclosure [Line Items]

Office lease, monthly rental rate

$ 72,525

$ 194,000

Embedded derivative financial instruments | Maximum

Commitments And Contingencies Disclosure [Line Items]

Other non-current liability

$ 5,000,000

Finisar Corp

Commitments And Contingencies Disclosure [Line Items]

Pending claims | claim

2

Lestina International Ltd. litigation

Commitments And Contingencies Disclosure [Line Items]

Damages sought, value

$ 3,000,000

APAT Arbitration

Commitments And Contingencies Disclosure [Line Items]

Damages sought, value

$ 1,500,000

Damages awarded to company

¥ 700

$ 110,000

Cisco Settlement Agreement [Member]

Commitments And Contingencies Disclosure [Line Items]

Loss contingency, damages awarded, value

150,000

300,000

Indemnification agreement

Commitments And Contingencies Disclosure [Line Items]

Payment for legal settlement

0

Lease termination

Commitments And Contingencies Disclosure [Line Items]

Asset retirement obligation

700,000

700,000

700,000

Performance guarantee | Private Placement

Commitments And Contingencies Disclosure [Line Items]

Other non-current liability

$ 7,500,000

$ 7,500,000

$ 7,500,000

$ 30,000,000

Scenario, Forecast | Russian federation

Commitments And Contingencies Disclosure [Line Items]

Exit fees for future

$ 2,000,000

Stockholders' equity - Narrativ

Stockholders' equity - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Class of Stock [Line Items]
Reclassified out of accumulated other comprehensive loss for realized gains or losses on available for sale securities	$ 0	$ 0	$ 0	$ 0
Accumulated deficit subject to restriction					$ 8,800
Minimum
Class of Stock [Line Items]
Accumulated profits					10.00%
Employee stock options
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	7,857,810		7,857,810
Employee stock purchase plan
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	644,187		644,187

Stockholders' equity - Accumula

Stockholders' equity - Accumulated Other Comprehensive Income (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance as of December 31, 2017			$ 194,451,000
Other comprehensive income (loss), net of taxes of zero and reclassifications	$ (5,588,000)	$ 2,178,000	(7,967,000)	$ 6,107,000
Balance as of September 30, 2018	161,174,000		161,174,000
Other comprehensive income (loss), tax			0
Foreign Currency Translation Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance as of December 31, 2017			567,000
Other comprehensive income (loss), net of taxes of zero and reclassifications			(7,968,000)
Balance as of September 30, 2018	(7,401,000)		(7,401,000)
Unrealized Gain (Loss) on Available-For-Sale Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance as of December 31, 2017			(1,000)
Other comprehensive income (loss), net of taxes of zero and reclassifications			1,000
Balance as of September 30, 2018	0		0
Defined Benefit Pension Plan Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance as of December 31, 2017			(168,000)
Other comprehensive income (loss), net of taxes of zero and reclassifications			0
Balance as of September 30, 2018	(168,000)		(168,000)
AOCI Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance as of December 31, 2017			398,000
Balance as of September 30, 2018	$ (7,569,000)		$ (7,569,000)

Stock-based compensation - Summ

Stock-based compensation - Summary of stock-based compensation expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation	$ 4,041	$ 1,934	$ 10,527	$ 5,692
Cost of goods sold
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation	553	340	1,832	811
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation	1,016	606	2,618	1,779
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation	931	393	2,511	1,170
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation	$ 1,541	$ 595	$ 3,566	$ 1,932

Stock-based compensation - Narr

Stock-based compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jul. 31, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in USD per share)				$ 6.80
Awards granted in the period (in shares)				1,355,262
Share-based compensation arrangement by share-based payment award, equity instruments other than options, vested in period				915,713
Shares outstanding (in shares)		2,630,138		2,630,138		2,404,637
Market-based restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in USD per share)				$ 5.82
Awards granted in the period (in shares)	665,000
Share-based compensation arrangement by share-based payment award, equity instruments other than options, vested in period				0
Stock Appreciation Units (SAUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted in the period (in shares)		0	0	0	0
Shares outstanding (in shares)		213,205		213,205		239,824
SAU-related liabilities		$ 1		$ 1		$ 0.8
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense		$ 0.1		$ 0.1

Stock-based compensation - Valu

Stock-based compensation - Valuation assumptions of stock-based awards (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Employee stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average expected term (years)	0 years	6 years	6 years 7 days	6 years
Weighted-average volatility	0.00%	65.00%	65.00%	65.00%
Risk-free interest rate	0.00%	2.02%
Risk-free interest rate minimum			2.27%	2.02%
Risk-free interest rate maximum			2.62%	2.08%
Expected dividends	0.00%	0.00%	0.00%	0.00%
Stock Appreciation Units (SAUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average expected term (years)	1 year 10 months 12 days	2 years 2 months 11 days	1 year 11 months 28 days	2 years 3 months 17 days
Weighted-average volatility	65.00%	71.00%	66.00%	71.00%
Risk-free interest rate minimum	1.73%	1.03%	1.03%	0.51%
Risk-free interest rate maximum	2.52%	1.55%	2.52%	1.55%
Expected dividends	0.00%	0.00%	0.00%	0.00%
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average expected term (years)	0 years	0 years	8 months 14 days	8 months
Weighted-average volatility	0.00%	0.00%	61.00%	55.00%
Risk-free interest rate	0.00%	0.00%
Risk-free interest rate minimum			1.20%	0.45%
Risk-free interest rate maximum			1.93%	0.91%
Expected dividends	0.00%	0.00%	0.00%	0.00%
Market-based restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average volatility	66.00%	0.00%	66.00%	0.00%
Risk-free interest rate	2.79%	0.00%	2.79%	0.00%
Expected dividends	0.00%	0.00%	0.00%	0.00%

Stock-based compensation - Stoc

Stock-based compensation - Stock Options and RSUs (Details)	9 Months Ended
	Sep. 30, 2018$ / sharesshares
Employee stock options
Number of Shares
Beginning Balance (in shares) | shares	3,933,529
Granted (in shares) | shares	158,116
Exercised/Converted (in shares) | shares	(591,322)
Cancelled/Forfeited (in shares) | shares	(95,251)
Ending Balance (in shares) | shares	3,405,072
Weighted Average Exercise Price
Beginning Balance (in USD per share) | $ / shares	$ 5.55
Granted (in USD per share) | $ / shares	6.64
Exercised/Converted (in USD per share) | $ / shares	4.33
Cancelled/Forfeited (in USD per share) | $ / shares	10.24
Ending Balance (in USD per share) | $ / shares	$ 5.68
Restricted stock units
Number of Units
Beginning Balance (in shares) | shares	2,404,637
Granted (in shares) | shares	1,355,262
Exercised/Converted (in shares) | shares	(915,713)
Cancelled/Forfeited (in shares) | shares	(214,048)
Ending Balance (in shares) | shares	2,630,138
Weighted Average Exercise Price
Beginning Balance (in USD per share) | $ / shares	$ 9.02
Granted (in USD per share) | $ / shares	6.80
Exercised/Converted (in USD per share) | $ / shares	9.02
Cancelled/Forfeited (in USD per share) | $ / shares	8.80
Ending Balance (in USD per share) | $ / shares	$ 7.89

Income taxes - Provision for in

Income taxes - Provision for income taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income tax (provision) benefit	$ (291)	$ 1,195	$ (2,009)	$ 1,813

Income taxes - Additional infor

Income taxes - Additional information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease to the amounts of uncertain tax positions previously determined	$ 0
Increase to the amounts of uncertain tax positions previously determined	$ 0
Accounting Standards Update 2016-16
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adjustments to accumulated deficit for new accounting pronouncements		$ 1,800

Subsequent events (Details)

Subsequent events (Details) - USD ($) $ in Millions	1 Months Ended
	Oct. 31, 2018	Aug. 31, 2018
Notes Payable CITIC Bank | Notes Payable to Banks
Subsequent Event [Line Items]
Repayments of lines of credit		$ 17
Line of Credit | Wells Fargo | Subsequent Event
Subsequent Event [Line Items]
Repayments of lines of credit	$ 5