GoPro (GPRO) 10-K 16 Feb 18 2017 FY Annual report Financial data

Document, Entity and Informatio

Document, Entity and Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Jan. 31, 2018	Jun. 30, 2017
Class of Stock [Line Items]
Entity Registrant Name	GoPro, Inc.
Entity Central Index Key	1,500,435
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 868,700,000,000
Common Class A [Member]
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		110,220,424
Common Class B [Member]
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		35,964,409

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 202,504	$ 192,114
Marketable securities	44,886	25,839
Accounts receivable, net	112,935	164,553
Inventory	150,551	167,192
Prepaid expenses and other current assets	62,811	38,115
Total current assets	573,687	587,813
Property and equipment, net	68,587	76,509
Intangible assets, net	24,499	33,530
Goodwill	146,459	146,459
Other long-term assets	37,014	78,329
Total assets	850,246	922,640
Current liabilities:
Accounts payable	138,257	205,028
Accrued liabilities	213,030	211,323
Deferred revenue	19,244	14,388
Total current liabilities	370,531	430,739
Long-term taxes payable	21,188	26,386
Long-term debt	130,048	0
Other long-term liabilities	29,774	18,570
Total liabilities	551,541	475,695
Commitments, contingencies and guarantees
Stockholders’ equity:
Preferred stock, $0.0001 par value, 5,000 shares authorized; none issued	0	0
Common stock and additional paid-in capital, $0.0001 par value, 500,000 Class A shares authorized, 101,034 and 104,647 shares issued and outstanding, respectively; 150,000 Class B shares authorized, 35,966 and 36,712 shares issued and outstanding, respectively	854,452	757,226
Treasury stock, at cost, 10,710 and 1,545 shares, respectively	(113,613)	(35,613)
Accumulated deficit	(442,134)	(274,668)
Total stockholders’ equity	298,705	446,945
Total liabilities and stockholders’ equity	$ 850,246	$ 922,640

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Sep. 30, 2016	Dec. 31, 2015
Preferred Stock, par value (usd per share)		$ 0.0001	$ 0.0001
Preferred Stock, Shares Authorized (shares)		5,000,000	5,000,000
Preferred Stock, Shares Issued (shares)		0	0
Common stock, par value (in dollars per share)		$ 0.0001	$ 0.0001
Treasury Stock, Shares (shares)		10,710,000	1,545,000
Common Class A [Member]
Common Stock, Shares Authorized (shares)	500,000,000	500,000,000	500,000,000
Common Stock, Shares, Issued (shares)	101,034,000		104,647,000
Common stock, shares, outstanding (shares)	101,000,000	101,034,000	104,647,000
Common Class B [Member]
Common Stock, Shares Authorized (shares)	150,000,000	150,000,000	150,000,000
Common Stock, Shares, Issued (shares)	35,966,000		36,712,000
Common stock, shares, outstanding (shares)	36,000,000	35,966,000	36,712,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Revenue	$ 1,179,741	$ 1,185,481	$ 1,619,971
Cost of revenue	795,211	723,561	946,757
Gross profit	384,530	461,920	673,214
Operating expenses:
Research and development	229,265	358,902	241,694
Sales and marketing	236,581	368,620	268,939
General and administrative	82,144	107,367	107,833
Total operating expenses	547,990	834,889	618,466
Operating income (loss)	(163,460)	(372,969)	54,748
Interest expense	(13,660)	(2,992)	(1,575)
Other income (expense), net	733	787	(588)
Total other expense, net	(12,927)	(2,205)	(2,163)
Income (loss) before income taxes	(176,387)	(375,174)	52,585
Income tax expense	6,486	43,829	16,454
Net Income (loss)	$ (182,873)	$ (419,003)	$ 36,131
Net income per share attributable to common stockholders - Basic (in dollars per share)	$ (1.32)	$ (3.01)	$ 0.27
Net income per share attributable to common stockholders - Diluted (in dollars per share)	$ (1.32)	$ (3.01)	$ 0.25
Weighted-average shares used to compute net income per share attributable to common stockholders - Basic (in shares)	138,056	139,425	134,595
Weighted-average shares used to compute net income per share attributable to common stockholders - Diluted (in shares)	138,056	139,425	146,486

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Cash Flows [Abstract]
Net income (loss)		$ (182,873)	$ (419,003)	$ 36,131
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization		41,478	41,640	28,981
Stock-based compensation		51,255	69,527	80,680
Excess tax benefit from stock-based compensation (1)		0	(3,463)	(29,348)
Deferred income taxes		(2,527)	38,568	(11,468)
Non-cash restructuring charges		7,315	17,601
Non-cash interest expense		5,345	0	0
Asset Impairment Charges		0	7,088	0
Other		4,094	7,574	5,427
Changes in operating assets and liabilities:
Accounts receivable, net		52,278	(18,816)	38,313
Inventory		16,641	21,040	(35,005)
Prepaid expenses and other assets		9,303	(14,618)	(23,281)
Accounts payable and other liabilities		(44,411)	142,941	68,461
Deferred revenue		5,249	2,168	(1,280)
Net cash provided by (used in) operating activities		(36,853)	(107,753)	157,611
Investing activities:
Purchases of property and equipment, net		(24,061)	(43,627)	(51,245)
Purchases of marketable securities		(52,318)	0	(220,055)
Maturities of marketable securities		21,659	119,918	94,680
Sale of marketable securities		11,623	47,348	30,048
Acquisitions, net of cash acquired		0	(104,353)	(65,405)
Net cash provided by (used in) investing activities		(43,097)	19,286	(211,977)
Financing activities:
Proceeds from issuance of common stock		9,751	9,664	36,775
Payments Related to Tax Withholding for Share-based Compensation		(12,118)	(6,889)	(13,942)
Proceeds from issuance of Convertible senior notes		175,000	0
Payments for Repurchase of Common Stock		(78,000)	0	(35,613)
Excess tax benefit from stock-based compensation (1)	[1]	0	3,463	29,348
Payment of deferred acquisition-related consideration		(75)	(950)
Payment of debt issuance costs		(5,964)	(3,333)	0
Payments of deferred public offering costs		0	0	(903)
Net cash provided by financing activities		88,594	1,955	15,665
Effect of exchange rate changes on cash and cash equivalents		1,746	(1,046)	(1,556)
Net increase (decrease) in cash and cash equivalents		10,390	(87,558)	(40,257)
Cash and cash equivalents at beginning of period		192,114	279,672	319,929
Cash and cash equivalents at end of period		202,504	192,114	279,672
Supplemental Cash Flow disclosure:
Cash paid (refunded) for income taxes, net		8,370	9,690	(1,093)
Cash paid for interest		3,114	0	0
Noncash Investing and Financing activities:
Purchases of property and equipment included in accounts payable and accrued liabilities		$ 5,785	$ 2,258	$ 5,153
[1]	Effective January 1, 2017, the Company adopted an accounting standard which addresses, among other items, updates to the presentation and treatment of excess tax benefits related to stock-based compensation. See Recent Accounting Standards in Note 1 below.

Consolidated Statements of Rede

Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) Statement - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock Including Additional Paid in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Special Termination Benefits [Member]	Special Termination Benefits [Member]Common Stock Including Additional Paid in Capital [Member]
Beginning Balance at Dec. 31, 2014	$ 641,204	$ 533,000	$ 0	$ 108,204
Beginning Balance (shares) at Dec. 31, 2014		129,115
Common stock issued under employee benefit plans, net of shares withheld for tax	36,413	$ 36,413
Common stock issued under employee benefit plans, net of shares withheld for tax (shares)		14,249
Taxes related to net share settlements	(13,943)	$ (13,943)
Retirement of common stock (shares)		(5,218)
Repurchase of outstanding common stock	(35,613)		(35,613)
Repurchase of outstanding common stock (shares)		(1,545)
Allocated share-based compensation expense	80,583	$ 80,583
Excess tax benefit from stock-based compensation	27,258	27,258
Net income (loss)	36,131			36,131
Ending Balance at Dec. 31, 2015	772,033	$ 663,311	(35,613)	144,335
Ending Balance (shares) at Dec. 31, 2015		136,601
Common stock issued under employee benefit plans, net of shares withheld for tax	10,103	$ 10,103
Common stock issued under employee benefit plans, net of shares withheld for tax (shares)		3,936
Taxes related to net share settlements	(6,889)	$ (6,889)
Shares issued to third-party vendor for services (Note 11)	7,297	$ 7,297
Shares issued to third-party vendor for services (Note 11) (shares)		822
Allocated share-based compensation expense	69,499	$ 69,499			$ 15,566	$ 15,566
Excess tax benefit from stock-based compensation	(1,661)	(1,661)
Net income (loss)	(419,003)			(419,003)
Ending Balance at Dec. 31, 2016	446,945	$ 757,226	(35,613)	(274,668)
Ending Balance (shares) at Dec. 31, 2016		141,359
Common stock issued under employee benefit plans, net of shares withheld for tax	9,732	$ 9,732
Common stock issued under employee benefit plans, net of shares withheld for tax (shares)		4,807
Taxes related to net share settlements	(12,118)	$ (12,118)
Allocated share-based compensation expense	54,037	54,037
Repurchase of common stock under Prepaid Forward contract (Note 5)	(78,001)	$ (1)	(78,000)
Repurchase of common stock under Prepaid Forward contract (Note 5) (shares)		(9,166)
Issuance of Convertible Note (Note 5)	45,211	$ 45,211
Cumulative effect of adoption of new ASU	15,772	365		15,407
Net income (loss)	(182,873)			(182,873)
Ending Balance at Dec. 31, 2017	$ 298,705	$ 854,452	$ (113,613)	$ (442,134)
Ending Balance (shares) at Dec. 31, 2017		137,000

Summary of business and signifi

Summary of business and significant accounting policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of significant accounting policies	Summary of business and significant accounting policies GoPro is enabling the way people capture and share their lives from a perspective only achieved with a GoPro. What began as an idea to help athletes document themselves engaged in sport, GoPro has become a mobile storytelling solution that helps the world share itself through immersive content. To date, our cameras and mountable and wearable accessories have generated substantially all of our revenue. We sell our products globally through retailers, wholesale distributors, and on our website. The Company’s global corporate headquarters are located in San Mateo, California. Basis of presentation. The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (GAAP). The Company’s fiscal year ends on December 31, and its fiscal quarters end on March 31, June 30 and September 30. Principles of consolidation. These consolidated financial statements include all the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Use of estimates. The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the amounts reported and disclosed in the Company’s consolidated financial statements and accompanying notes. Significant estimates and assumptions made by management include those related to revenue recognition (including sales returns, implied post contract support, price protection and other sales incentives), stock-based compensation, inventory valuation, product warranty liabilities, the valuation and useful lives of long-lived assets (property and equipment, intangible assets and goodwill) and income taxes. The Company bases its estimates and assumptions on historical experience and on various other factors that it believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results could differ materially from management’s estimates. To the extent there are material differences between the estimates and the actual results, future results of operations could be affected. Comprehensive income (loss). For all periods presented, comprehensive income (loss) approximated net income (loss). Therefore, the consolidated statements of comprehensive income (loss) have been omitted. Prior period reclassifications. Reclassifications of certain prior period amounts in the consolidated financial statements have been made to conform to the current period presentation. Cash equivalents and marketable securities. Cash equivalents primarily consist of investments in money market funds with maturities of three months or less from the date of purchase. Marketable securities consist of commercial paper, U.S. agency securities, and corporate debt securities, and are classified as available-for-sale securities. The Company views these securities as available to support current operations and it has classified all available-for-sale securities as current assets. Available-for-sale securities are carried at fair value with unrealized gains and losses, if any, included in stockholders’ equity. Unrealized losses are charged against other income (expense), net, for declines in fair value below the cost of an individual investment that is deemed to be other than temporary. The Company has not identified any marketable securities as other-than-temporarily impaired for the periods presented. The cost of securities sold is based upon a specific identification method. Accounts receivable and allowance for doubtful accounts. Accounts receivable are stated at invoice value less estimated allowances for returns and doubtful accounts. Allowances are recorded based on the Company’s assessment of various factors, such as: historical experience, credit quality of its customers, age of the accounts receivable balances, geographic related risks, economic conditions and other factors that may affect a customer’s ability to pay. The allowance for doubtful accounts as of December 31, 2017 and 2016 was $0.8 million and $1.3 million , respectively. Inventory. Inventory consists of finished goods and component parts, which are purchased directly from suppliers or from contract manufacturers. Inventory is stated at the lower of cost or net realizable value on a first-in, first-out basis. The Company writes down its inventory for estimated obsolescence or excess inventory equal to the difference between the cost of inventory and estimated market value. The Company’s assessment of market value is based upon assumptions around market conditions and estimated future demand for its products within a specified time horizon, generally 12 months. Adjustments to reduce inventory to net realizable value are recognized in cost of revenue. Point of purchase (POP) displays. The Company provides retailers with POP displays, generally free of charge, in order to facilitate the marketing of the Company’s products within retail stores. The POP displays contain a display that broadcasts video images taken by GoPro cameras with product placement available for cameras and accessories. POP display costs, less any fees charged, are capitalized as long-term assets and charged to sales and marketing expense over the expected period of benefit, which generally ranges from 24 to 36 months . Cash outflows and amortization related to POP displays are classified as operating activities in the consolidated statement of cash flows. Amortization was $19.2 million , $19.6 million and $16.8 million in 2017 , 2016 and 2015 , respectively. Property and equipment, net. Property and equipment are stated at cost and are depreciated using the straight-line method over the estimated useful life of the assets, ranging from one to eleven years. Leasehold improvements are amortized over the shorter of the lease term or their expected useful life. Property and equipment pending installation, configuration or qualification are classified as construction in progress. Costs of maintenance and repairs that do not improve or extend the lives of the respective assets are expensed as incurred. Fair value measurements. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the reporting date. The Company estimates and categorizes the fair value of its financial assets by applying the following hierarchy: Level 1 Valuations based on quoted prices in active markets for identical assets or liabilities that the Company has the ability to directly access. Level 2 Valuations based on quoted prices for similar assets or liabilities; valuations for interest-bearing securities based on non-daily quoted prices in active markets; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable data for substantially the full term of the assets or liabilities. Level 3 Valuations based on inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The fair value of Level 2 financial instruments is obtained from an independent pricing service, which may use quoted market prices for identical or comparable instruments or model driven valuations using observable market data or inputs corroborated by observable market data. Leases. The Company leases its office space and facilities under cancelable and non-cancelable operating leases. For leases that contain rent escalation or rent concession provisions, the Company recognizes rent expense on a straight-line basis over the term of the lease. The Company does not assume renewals in its determination of the lease term unless the renewals are deemed to be reasonably assured at lease inception. The Company also calculates a liability for costs that will continue to be incurred under a lease for its remaining term without economic benefit to the Company upon determination of a cease-use date. The fair value of the liability is determined based on remaining lease payments, estimated sublease income and the effects of any prepaid or deferred items recognized under the lease. Goodwill and other intangible assets. Goodwill represents the excess of the purchase price over the fair value of the net assets acquired in a business combination. Acquired intangible assets other than goodwill are amortized over their useful lives unless the lives are determined to be indefinite. For intangible assets acquired in a business combination, the estimated fair values of the assets received are used to establish their recorded values. Valuation approaches consistent with the market approach, income approach and/or cost approach are used to measure fair value. Impairment of goodwill and long-lived assets. The Company performs an annual assessment of its goodwill during the fourth quarter of each calendar year or more frequently if indicators of potential impairment exist, such as an adverse change in business climate or a decline in the overall industry demand, that would indicate it is more likely than not that the fair value of its single reporting unit is less than its carrying value. There was no impairment of goodwill recorded for any periods presented. For annual impairment testing in 2017 , the Company performed a quantitative analysis and determined the fair value of its single reporting unit exceeded the carrying value. Other indefinite-lived intangible assets are assessed for impairment at least annually. If their carrying value exceeds the estimated fair value, the difference is recorded as an impairment. See Note 4 for information regarding impairment charges recorded for indefinite-lived intangible assets. Long-lived assets, such as property and equipment and intangible assets subject to amortization, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset group may not be recoverable. Recoverability of assets to be held and used is measured by comparing the carrying amount to the estimated future undiscounted cash flows expected to be generated by the asset group. If it is determined that an asset group is not recoverable, an impairment charge is recognized for the amount by which the carrying amount of the asset group exceeds its fair value. There was no material impairment of long-lived assets for any periods presented. Warranty. The Company records a liability for estimated product warranty costs at the time product revenue is recognized. The Company’s standard warranty obligation to its end-users generally provides a 12 -month warranty coverage on all of its products except in the European Union where the Company provides a 2 -year warranty. An extended warranty is also available for a fee. The Company’s estimate of costs to service its warranty obligations is based on its historical experience of repair and replacement of the associated products and expectations of future conditions. The warranty obligation is affected by product failure rates and the related use of materials, labor costs and freight incurred in correcting any product failure. Revenue recognition. Revenue is primarily comprised of product revenue, net of returns and sales incentives. The Company derives substantially all of its revenue from the sale of cameras, drones, mounts and accessories and the related implied post contract support (PCS). The Company recognizes revenue when persuasive evidence of an arrangement exists, delivery has occurred, the sales price is fixed or determinable, and collectability is reasonably assured. For most of the Company’s revenue, these criteria are met at the time the product is shipped. For customers who purchase products directly from the Company’s website, revenue is deferred until delivery to the customer’s address because the Company retains a portion of the risk of loss on these sales during transit. The Company's standard terms and conditions of sale for non-web based sales do not allow for product returns other than under warranty. However, the Company grants limited rights to return product for certain large retailers and distributors. Estimates of expected future product returns are recognized at the time of sale based on analyses of historical return trends by customer class. Upon recognition, the Company reduces revenue and cost of sales for the estimated returns. Return trends are influenced by product life cycles, new product introductions, market acceptance of products, product sell-through, the type of customer, seasonality and other factors. Return rates may fluctuate over time, but are sufficiently predictable to allow the Company to estimate expected future product returns. The Company’s camera sales are multiple element arrangements that generally include the following three separate units of accounting: a) a hardware component (camera, drone and/or accessories) and the embedded firmware essential to the functionality of the hardware component delivered at the time of sale, b) the implicit right to the Company's downloadable free apps and software solutions (GoPro and Quik apps), and c) the implied right for the customer to receive PCS. PCS includes the right to receive, on a when and if available basis, future unspecified firmware upgrades and features as well as bug fixes, and email and telephone support. The Company accounts for each element separately and allocates revenue based on its best estimate of the selling price (BESP). The Company’s process for determining BESP considers multiple factors that may vary over time depending upon the unique facts and circumstances related to each deliverable, including: the level of support provided to customers, estimated costs to provide the Company’s support, the amount of time and cost that is allocated to the Company’s efforts to develop the undelivered elements, and market trends in the pricing for similar offerings. Revenue allocated to the delivered hardware, related essential software and free software is recognized at the time of sale provided the conditions for recognition of revenue have been met. Revenue allocated to PCS is deferred and recognized on a straight-line basis over the estimated term of the support period, which is estimated to be 15 months based on historical experience. Deferred revenue also includes amounts related to the Company’s GoPro Care and GoPro Plus fee-based service offerings. Sales incentives. The Company offers sales incentives through various programs, including cooperative advertising, marketing development funds and other incentives. Sales incentives are recorded as a reduction to revenue in the period the incentives are offered to the Company’s customers or the related revenue is recognized, whichever is later. In addition, the Company offers price protection discounts to certain customers, which are recorded as a reduction of revenue at the date of sale. Shipping costs. Amounts billed to customers for shipping and handling are classified as revenue and the Company’s related shipping and handling costs incurred are classified as cost of revenue. Sales taxes. Sales taxes collected from customers and remitted to respective governmental authorities are recorded as liabilities and are not included in revenue. Advertising costs. Advertising costs consist of costs associated with print, television and e-commerce media advertisements and are expensed as incurred. The Company incurs promotional expenses resulting from payments under event, resort and athlete sponsorship contracts. These sponsorship arrangements are considered to be executory contracts and, as such, the costs are expensed as performance under the contract is received. The costs associated with preparation of sponsorship activities, including the supply of GoPro products, media team support, and activation fees are expensed as incurred. Prepayments made under sponsorship agreements are included in prepaid expenses or other long-term assets depending on the period to which the prepayment applies. Advertising costs were $61.3 million , $106.0 million and $64.7 million in 2017 , 2016 and 2015 , respectively. Stock-based compensation. The Company accounts for stock-based compensation in accordance with accounting guidance that requires all stock-based awards granted to employees and directors to be measured at fair value and recognized as an expense. The Company primarily issues restricted stock units and accounts for forfeitures as they occur. For service-based awards, stock-based compensation is recognized on a straight-line basis over the requisite service period. For performance and market-based awards which also require a service period, the Company uses graded vesting over the longer of the derived service period or when the performance or market condition is satisfied. Foreign currency. The U.S. dollar is the functional currency of the Company’s foreign subsidiaries. The Company remeasures monetary assets or liabilities denominated in currencies other than the U.S. dollar using exchange rates prevailing on the balance sheet date, and non-monetary assets and liabilities at historical rates. Foreign currency remeasurement and transaction gains and losses are included in other income (expense), net and have not been material for any periods presented. Income taxes. The Company utilizes the asset and liability method for computing its income tax provision, under which deferred tax assets and liabilities are recognized for the expected future consequences of temporary differences between the financial reporting and tax bases of assets and liabilities using enacted tax rates. Management makes estimates, assumptions and judgments to determine the Company’s provision for income taxes, deferred tax assets and liabilities, and any valuation losses recorded against deferred tax assets. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent the Company believes recovery is not likely, establishes a valuation allowance. The Company recognizes the tax benefit from an uncertain tax position only if it is more likely than not the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The tax benefits recognized from such positions are then measured based on the largest benefit that has a greater than 50% likelihood of being realized upon settlement. Interest and penalties related to unrecognized tax benefits are recognized within income tax expense. On December 22, 2017, the President of the United States signed into law the Tax Cuts and Jobs Act (TCJA). Further information on the tax impacts of the TCJA is included in Note 9 of the Company’s consolidated financial statements. Segment information. The Company operates as one operating segment as it only reports financial information on an aggregate and consolidated basis to its CEO, who is the Company’s chief operating decision maker. Recent accounting standards Standard Description Date of adoption Effect on the financial statements or other significant matters Standards that were adopted Stock Compensation This standard simplifies certain aspects of the accounting for share-based payment transactions, including income taxes, classification of awards and classification on the statement of cash flows. The new guidance also allows an entity to make a policy election to account for forfeitures as they occur. January 1, 2017 Adoption of the standard resulted in the recognition of previously unrecognized excess tax benefits using the modified retrospective method. The Company recorded an increase to U.S. deferred tax assets of $179 million which was recorded directly against the accumulated deficit. The increased deferred tax asset allowed for an offset against long-term income tax payable of $16 million. A full valuation allowance was provided on the remaining U.S. deferred tax asset of $163 million, which was also recorded against the accumulated deficit. The net impact to equity was a decrease in the accumulated deficit of approximately $16 million. The Company elected to apply the change in presentation to the statements of cash flows prospectively and elected to account for forfeitures as they occur. Standards not yet adopted Revenue from Contracts with Customers ASU No. 2014-09, 2015-14, 2016-08, 2016-10 and 2016-12 (Topic 606) The updated revenue standard establishes principles for recognizing revenue and develops a common revenue standard for all industries. Under the new model, recognition of revenue occurs when a customer obtains control of promised goods or services in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The new standard requires that entities disclose the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Early adoption is permitted, but not earlier than the first quarter of 2017. The retrospective or cumulative effect transition method is permitted. January 1, 2018 The Company completed an analysis of the impact of the standard on its sales contract portfolio by reviewing its current accounting policies and practices to identify differences that would result from applying the requirements of the new standard to its sales contracts. The Company’s analysis of its contracts under the new standard supports the recognition of its product revenue at the time product is shipped, consistent with its current revenue policy. As a result of the adoption of the new guidance, certain sales incentives will need to be estimated as variable consideration at the time product is shipped and included as a reduction to the transaction price. This will result in a reduction of revenue being recorded earlier than under the existing guidance. Additionally, for customers who purchase products directly from the Company's website, the new standard provides for a policy election whereby the Company will record revenue when the related product is shipped. This will result in recognition of revenue earlier than under existing guidance, under which the Company recognizes revenue upon delivery to the customer. The Company expects the net impact of ASU 2014-09 to be less than $5 million as a reduction to retained earnings. The Company will adopt the standard on a modified retrospective basis. Leases ASU No. 2016-02(Topic 842) This standard requires lessees to put most leases on their balance sheets but recognize the expenses on their income statements in a manner similar to current practice. Lessees would recognize a right-to-use asset and lease liability for all leases with terms of more than 12 months. The new standard should be applied on a modified retrospective basis. January 1, 2019 Although the Company is currently evaluating the impact that the adoption of this standard will have on its consolidated financial statements and related disclosures, the Company currently expects that most of its operating lease commitments will be subject to the new standard and recognized as operating lease liabilities and right-of-use assets upon adoption. Income Taxes ASU No. 2016-16 (Topic 740) This standard requires entities to recognize the income tax consequences of intra-entity asset transfers when they occur. This removes the exception to postpone recognition until the asset has been sold to an outside party. The updated standard is effective in annual and interim periods in fiscal years beginning after December 15, 2017, with early adoption permitted during the first interim period of a fiscal year. January 1, 2018 The Company intends to apply the modified retrospective approach upon adoption. The Company expects that the adoption of ASU 2016-16 on January 1, 2018 will result in a $15 million cumulative-effect increase in accumulated deficit on its consolidated financial statements and related disclosures. Intangible - Goodwill and Other ASU No. 2017-04 (Topic 350) This standard simplifies the accounting for goodwill and removes Step 2 of the annual goodwill impairment test. Upon adoption, goodwill impairment will be determined based on the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. Early adoption permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017, and requires a prospective transition method. January 1, 2020 The Company does not expect that the adoption of this standard will have a material impact on its consolidated financial statements and related disclosures. Stock Compensation This standard clarifies when to account for a change to the terms or conditions of a share-based payment award as a modification. Under this standard, modification is required only if the fair value, the vesting conditions, or the classification of an award as equity or liability changes as a result of the change in terms or conditions. The updated standard is effective in annual and interim periods in fiscal years beginning after December 15, 2017, with early adoption permitted. January 1, 2018 The Company does not expect that the adoption of ASU 2017-09 will have a material impact to its consolidated financial statements and related disclosures. The Company will adopt the amendment on a prospective basis. Although there are several other new accounting standards issued or proposed by the FASB, which the Company has adopted or will adopt, as applicable, the Company does not believe any of these additional accounting pronouncements has had or will have a material impact on its financial statements.

Business Acquisitions

Business Acquisitions	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business acquisitions	Business Acquisitions In 2016, the Company completed acquisitions of two privately-held mobile editing application companies for total cash consideration of approximately $104 million . The aggregate allocation of the purchase prices primarily included $17.4 million of identifiable intangible assets, $3.4 million of net deferred tax liabilities and approximately $89 million of residual goodwill. Net tangible assets acquired were not material. In addition to the amounts above, aggregate deferred cash and stock compensation of up to approximately $35 million is payable to certain continuing employees subject to meeting specified future employment conditions. This amount is being recognized as compensation expense over the requisite service periods of up to four years from the respective acquisition dates, including approximately $22 million recognized in 2016. In 2015, the Company completed several acquisitions qualifying as business combinations for aggregate consideration of $70.2 million , the substantial majority of which was cash consideration. The aggregated allocation of the purchased prices primarily included $32.3 million of identifiable intangible assets, $4.7 million of net deferred tax liabilities and approximately $43.0 million of residual goodwill. Net liabilities assumed were not material. Goodwill is primarily attributable to expected synergies in the technologies that can be leveraged by the Company in future product offerings related to device and software related offerings. Goodwill is not expected to be deductible for U.S. income tax purposes. The operating results of the acquired companies have been included in the Company's consolidated financial statements for 2016 and 2015 from the date of acquisition. Actual and pro forma results of operations for these acquisitions have not been presented because they did not have a material impact to the Company's consolidated results of operations, either individually or in aggregate.

Fair value measurements

Fair value measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value measurements	Fair value measurements The Company’s assets that are measured at fair value on a recurring basis within the fair value hierarchy are summarized as follows: December 31, 2017 December 31, 2016 (in thousands) Level 1 Level 2 Total Level 1 Level 2 Total Cash equivalents (1) : Money market funds $ 25,251 $ — $ 25,251 $ 18,024 $ — $ 18,024 Commercial paper 14,981 — 14,981 — — — Corporate debt securities — 2,500 2,500 — — — Agency securities 4,999 4,999 — — — Total cash equivalents $ 40,232 $ 7,499 $ 47,731 $ 18,024 $ — $ 18,024 Marketable securities: U.S. treasury securities $ — $ 4,995 $ 4,995 $ — $ 8,283 $ 8,283 Commercial paper 19,888 — 19,888 — — — Corporate debt securities — 20,003 20,003 — 15,226 15,226 Municipal securities — — — — 2,330 2,330 Total marketable securities $ 19,888 $ 24,998 $ 44,886 $ — $ 25,839 $ 25,839 (1) Included in cash and cash equivalents in the accompanying consolidated balance sheets. Cash balances were $154.8 million and $174.1 million as of December 31, 2107 and 2016, respectively. There were no transfers of financial assets between levels for the periods presented. Cash equivalents and marketable securities are classified as Level 1 or Level 2 because the Company uses quoted market prices or alternative pricing sources and models utilizing market observable inputs to determine their fair value. The contractual maturities of available-for-sale marketable securities as of December 31, 2017 and 2016 were all less than one year in duration. At December 31, 2017 and 2016 , the Company had no financial assets or liabilities that were classified as Level 3, which are valued based on inputs supported by little or no market activity. At December 31, 2017 and 2016 , the amortized cost of the Company’s cash equivalents and marketable securities approximated their fair value and there were no material realized or unrealized gains or losses, either individually or in the aggregate. The Company’s liabilities that are disclosed but not measured at fair value include the Convertible Senior Notes (see Note 5, Financing Arrangements). The fair value measurement is classified as Level 2 within the fair value hierarchy since it is based on quoted market prices of the Company’s instruments in markets that are not active. The Company estimated the fair value of the Notes by evaluating quoted market prices and calculating the upfront cash payment a market participant would require to assume these obligations. The upfront cash payment used in the calculations of fair value on December 31, 2017 , excluding any issuance costs, is the amount that a market participant would be willing to lend at December 31, 2017 to an entity with a credit rating similar to the Company and achieve sufficient cash inflows to cover the scheduled cash outflows. The calculated fair value of the Notes, of $172.2 million , is highly correlated to the Company’s stock price and as a result, significant changes to stock price will have a significant impact on the calculated fair value of the Notes. For certain other financial assets and liabilities, including accounts receivable, accounts payable and other current liabilities, the carrying amounts approximate their fair value due to the relatively short maturity of these balances.

Condensed consolidated financia

Condensed consolidated financial statement details Condensed consolidated financial statement details	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Consolidated financial statement details	onsolidated financial statement details The following sections and tables provide details of selected balance sheet items. Inventory (in thousands) December 31, 2017 December 31, 2016 Components $ 18,995 $ 25,236 Finished goods 131,556 141,956 Total inventory $ 150,551 $ 167,192 Property and equipment, net (in thousands) Useful life (in years) December 31, 2017 December 31, 2016 Leasehold improvements 1–11 $ 67,713 $ 48,103 Production, engineering and other equipment 4 47,502 46,328 Tooling 1–2 24,871 23,742 Computers and software 2 20,636 18,750 Furniture and office equipment 3 14,895 12,530 Tradeshow equipment and other 2–5 7,237 7,578 Construction in progress 347 1,870 Gross property and equipment 183,201 158,901 Less: Accumulated depreciation and amortization (114,614 ) (82,392 ) Property and equipment, net $ 68,587 $ 76,509 Depreciation expense was $32.4 million in 2017 and 2016 , and $24.8 million in 2015 . In 2017 and 2016, the Company recorded accelerated depreciation charges in connection with its plans to vacate certain leased office facilities as disclosed in Note 11. Intangible assets Useful life (in months) December 31, 2017 (in thousands) Gross carrying value Accumulated amortization Net carrying value Purchased technology 24–72 $ 49,901 $ (26,017 ) $ 23,884 In-process research and development (IPR&D) 615 — 615 Total intangible assets $ 50,516 $ (26,017 ) $ 24,499 Useful life (in months) December 31, 2016 (in thousands) Gross carrying value Accumulated Net carrying value Purchased technology 24–72 $ 47,001 $ (17,086 ) $ 29,915 IPR&D 3,615 — 3,615 Total intangible assets $ 50,616 $ (17,086 ) $ 33,530 In 2017, the Company did not record any impairment charges for IPR&D assets. In 2016, the Company recorded impairment charges of $6.3 million to research and development expense for abandoned IPR&D assets. As of December 31, 2017 , technological feasibility has not been established for the remaining IPR&D assets, which have no alternative future use and, as such, continue to be accounted for as indefinite-lived intangible assets. Amortization expense was $9.0 million , $9.1 million and $4.2 million in 2017 , 2016 and 2015 , respectively. At December 31, 2017 , expected amortization expense of intangible assets with definite lives for future periods is as follows: (in thousands) Total Year ending December 31, 2018 $ 9,263 2019 8,753 2020 4,998 2021 870 2022 — $ 23,884 Other long-term assets (in thousands) December 31, 2017 December 31, 2016 POP displays $ 16,451 $ 27,592 Long-term deferred tax assets 825 106 Income tax receivable — 33,425 Deposits and other 19,738 17,206 Other long-term assets $ 37,014 $ 78,329 Accrued liabilities (in thousands) December 31, 2017 December 31, 2016 Accrued payables (1) $ 44,582 $ 91,655 Employee related liabilities (1) 24,945 42,577 Accrued sales incentives 89,549 40,070 Warranty liability 9,934 11,456 Customer deposits 8,700 4,381 Income taxes payable 1,247 2,756 Purchase order commitments 6,162 4,730 Inventory received 14,470 3,950 Other 13,441 9,748 Accrued liabilities $ 213,030 $ 211,323 (1) See Note 13 for amounts associated with restructuring liabilities. Product warranty The following table summarizes the warranty liability activity: Year ended December 31, (in thousands) 2017 2016 2015 Beginning balances $ 11,945 $ 10,856 $ 6,405 Charged to cost of revenue 20,139 19,272 25,377 Settlements of warranty claims (21,711 ) (18,183 ) (20,926 ) Ending balances $ 10,373 $ 11,945 $ 10,856 At December 31, 2017, $9.9 million of the warranty liability was recorded as an element of accrued liabilities and $0.4 million was recorded as an element of other long-term liabilities.

Financing Arrangements

Financing Arrangements	12 Months Ended
	Dec. 31, 2017
Line of Credit Facility [Line Items]
Financing Arrangements	Financing Arrangements Credit Facility In March 2016, the Company entered into a Credit Agreement (Credit Agreement) with certain banks which provides for a secured revolving credit facility (Credit Facility) under which the Company may borrow up to an aggregate of $250.0 million . The Company and its lenders may increase the total commitments under the Credit Facility to up to $300.0 million , subject to certain conditions. The Credit Facility will terminate and all outstanding borrowings become due and payable in March 2021. The amount that may be borrowed under the Credit Facility is determined at periodic intervals and is based upon the Company’s inventory and accounts receivable balances. Borrowed funds accrue interest, at the Company’s election, based on an annual rate of (a) London Interbank Offered Rate (LIBOR) or (b) the administrative agent’s base rate, plus an applicable margin of between 1.50% and 2.00% for LIBOR rate loans, and between 0.50% and 1.00% for base rate loans. The Company is required to pay a commitment fee on the unused portion of the Credit Facility of 0.25% or 0.375% per annum, based on the level of utilization of the Credit Facility. Amounts owed under the Credit Agreement and related credit documents are guaranteed by the Company and its material subsidiaries. The Company and its Cayman and Netherlands subsidiaries have also granted security interests in substantially all of their assets to collateralize this obligation. The Credit Agreement contains customary covenants, such as financial statement reporting requirements and limiting the ability of the Company and its subsidiaries to pay dividends or incur debt, create liens and encumbrances, make investments, and redeem or repurchase stock. The Company is required to maintain a minimum fixed charge coverage ratio if and when the unborrowed availability under the Credit Facility is less than the greater of $25.0 million or 10.0% of the borrowing base at such time. The Credit Agreement also contains customary events of default, such as the failure to pay obligations when due, initiation of bankruptcy or insolvency proceedings, or defaults on certain other indebtedness. Upon an event of default, the lenders may, subject to customary cure rights, require the immediate payment of all amounts outstanding and foreclose on collateral. At December 31, 2017 and 2016 , the Company could borrow up to approximately $118.0 million and $150.0 million , respectively, under the Credit Facility, and was in compliance with all financial covenants contained in the Credit Agreement. The Company has made no borrowings from the Credit Facility to date. Convertible Notes In April 2017, the Company issued $175.0 million aggregate principal amount of 3.50% Convertible Senior Notes due 2022 (Notes). The Notes are senior, unsecured obligations of GoPro and mature on April 15, 2022 (Maturity Date), unless earlier repurchased or converted into shares of Class A common stock under certain circumstances described below. The Notes are convertible into cash, shares of the Company’s Class A common stock, or a combination thereof, at the Company’s election, at an initial conversion rate of 94.0071 shares of Class A common stock per $1,000 principal amount of the Notes, which is equivalent to an initial conversion price of approximately $10.64 per share of common stock, subject to adjustment. The Company currently has the intent and ability to deliver cash up to the principal amount of the Notes then outstanding upon conversion. The Company will pay interest on the Notes semi-annually in arrears on April 15 and October 15 of each year. The $175.0 million of proceeds received from the issuance of the Notes were allocated between long-term debt (the liability component) of $128.3 million and additional paid-in-capital (the equity component) of $46.7 million on the consolidated balance sheet. The fair value of the liability component was measured using rates determined for similar debt instruments without a conversion feature. The carrying amount of the equity component, representing the conversion option, was determined by deducting the fair value of the liability component from the aggregate face value of the Notes. The liability component will be accreted up to the face value of the Notes of $175.0 million , which will result in additional non-cash interest expense being recognized in the consolidated statements of operations through the Notes’ Maturity Date. The effective interest rate on the Notes, including accretion of the notes to par and debt issuance cost amortization, was approximately 10.5% . The equity component will not be remeasured as long as it continues to meet the conditions for equity classification. The Company incurred approximately $5.7 million of issuance costs related to the issuance of the Notes, of which $4.2 million and $1.5 million were recorded to long-term debt and additional paid-in capital, respectively. The $4.2 million of issuance costs recorded as long-term debt on the consolidated balance sheet are being amortized over the five-year contractual term of the Notes using the effective interest method. The Company may not redeem the Notes prior to the Maturity Date and no sinking fund is provided for the Notes. The Indenture includes customary terms and covenants, including certain events of default after which the Notes may be due and payable immediately. Holders have the option to convert the Notes in multiples of $1,000 principal amount at any time prior to January 15, 2022, but only in the following circumstances: • during any calendar quarter beginning after the calendar quarter ending on September 30, 2017, if the last reported sale price of Class A common stock for at least 20 trading days (whether or not consecutive) during the last 30 consecutive trading days of the immediately preceding fiscal quarter is greater than or equal to 130% of the conversion price of the Notes on each applicable trading day; • during the five-business day period following any five consecutive trading day period in which the trading price for the Notes is less than 98% of the product of the last reported sale price of Class A common stock and the conversion rate for the Notes on each such trading day; or • upon the occurrence of specified corporate events. At any time on or after January 15, 2022 until the second scheduled trading day immediately preceding the Maturity Date of the Notes on April 22, 2022, a holder may convert its Notes, in multiples of $1,000 principal amount. Holders of the Notes who convert their Notes in connection with a make-whole fundamental change (as defined in the Indenture) are, under certain circumstances, entitled to an increase in the conversion rate. In addition, in the event of a fundamental change prior to the Maturity Date, holders will, subject to certain conditions, have the right, at their option, to require the Company to repurchase for cash all or part of the Notes at a repurchase price equal to 100% of the principal amount of the notes to be repurchased, plus accrued and unpaid interest up to, but excluding, the repurchase date. As of December 31, 2017 , the outstanding principal on the Notes was $175.0 million , the unamortized debt discount was $41.4 million , the unamortized debt issuance cost was $3.6 million and the net carrying amount of the liability component was $130.0 million , which was recorded as long-term debt within the consolidated balance sheet. For the year ended December 31, 2017 , the Company recorded interest expense of $4.4 million for contractual coupon interest, $0.6 million for amortization of debt issuance costs, and $5.3 million for amortization of the debt discount. In connection with the offering, the Company entered into a prepaid forward stock repurchase transaction (Prepaid Forward) with a financial institution (Forward Counterparty). Pursuant to the Prepaid Forward, the Company used approximately $78.0 million of the net proceeds from the offering of the Notes to fund the Prepaid Forward. The aggregate number of shares of the Company’s Class A common stock underlying the Prepaid Forward was approximately 9.2 million . The expiration date for the Prepaid Forward is April 15, 2022, although it may be settled earlier in whole or in part. Upon settlement of the Prepaid Forward, at expiration or upon any early settlement, the Forward Counterparty will deliver to the Company the number of shares of Class A common stock underlying the Prepaid Forward or the portion thereof being settled early. The shares purchased under the Prepaid Forward are treated as treasury stock on the consolidated balance sheet (and not outstanding for purposes of the calculation of basic and diluted earnings per share), but will remain outstanding for corporate law purposes, including for purposes of any future stockholders’ votes, until the Forward Counterparty delivers the shares underlying the Prepaid Forward to the Company. The Company’s Prepaid Forward hedge transaction exposes the Company to credit risk to the extent that its counterparty may be unable to meet the terms of the transaction. The Company mitigates this risk by limiting its counterparty to a major financial institution.

Stockholders' equity

Stockholders' equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Stockholders' Equity	Stockholders’ equity Common stock. The Company has two classes of authorized common stock: Class A common stock with 500 million shares authorized and Class B common stock with 150 million shares authorized. As of December 31, 2017 , 101.0 million shares of Class A stock were issued and outstanding and 36.0 million shares of Class B stock were issued and outstanding. The rights of the holders of Class A and Class B common stock are identical, except with respect to voting power and conversion rights. Each share of Class A common stock is entitled to one vote per share and each share of Class B common stock is entitled to ten votes per share. Each share of Class B common stock is convertible at any time at the option of the stockholder into one share of Class A common stock and has no expiration date. The Class B common stock is also convertible into Class A common stock on the same basis upon any transfer, whether or not for value, except for “permitted transfers” as defined in the Company’s restated certificate of incorporation. Each share of Class B common stock will convert automatically into one share of Class A common stock upon the date when the outstanding shares of Class B common stock represent less than 10% of the aggregate number of shares of common stock then outstanding. As of December 31, 2017 , the Class B stock continued to represent greater than 10% of the overall outstanding shares. The Company had the following shares of common stock reserved for issuance upon the exercise of equity instruments as of December 31, 2017: (in thousands) December 31, 2017 Stock options outstanding 9,809 Restricted stock units outstanding 9,483 Common stock available for future grants 23,071 Total common stock shares reserved for issuance 42,363 Stock repurchase program . The stock repurchase program authorized by the Company’s board of directors in September 2015 to repurchase up to $300 million of the Company’s Class A common stock expired on September 30, 2016 and has not been renewed. The repurchase program did not obligate the Company to acquire any specific number of shares. Under the program, the Company repurchased approximately 1.5 million shares of its common stock at an average price of $23.05 per share, for an aggregate purchase price of approximately $35.6 million . The Company holds the repurchased shares as treasury stock. CEO stock contributions. In the first half of 2015, the CEO contributed an aggregate 5.2 million common stock to the Company without consideration per the terms of a Contribution Agreement dated December 28, 2011, and amended on May 11, 2015. Under the original Contribution Agreement, the CEO agreed to contribute back to the Company from time-to-time the same number of shares of common stock as are issued to a certain Company employee upon the exercise of certain stock options held by such employee. Pursuant to this agreement, the CEO contributed back to the Company 0.5 million shares of Class B common stock from January 2015 through April 2015. In May 2015, the CEO contributed back to the Company 4.7 million shares of Class B common stock pursuant to the amended agreement, representing all of the then remaining shares subject to the contribution obligations. All of the shares contributed by the CEO were retired during the year.

Employee benefit plans

Employee benefit plans	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Employee benefit plans	Employee benefit plans Equity incentive plans . The Company has outstanding equity grants from its three stock-based employee compensation plans: the 2014 Equity Incentive Plan (2014 Plan), the 2010 Equity Incentive Plan (2010 Plan) and the 2014 Employee Stock Purchase Plan (ESPP). No new options or awards have been granted under the 2010 Plan since June 2014. Outstanding options and awards under the 2010 Plan continue to be subject to the terms and conditions of the 2010 Plan. The 2014 Plan serves as the successor to the 2010 Plan and provides for the granting of incentive and nonqualified stock options, restricted stock awards (RSAs), restricted stock units (RSUs), stock appreciation rights, stock bonus awards and performance awards to qualified employees, non-employee directors and consultants. Options granted under the 2014 Plan generally expire within 10 years from the date of grant and generally vest over one to four years. RSUs granted under the 2014 Plan generally vest over two to four -years based upon continued service and are settled at vesting in shares of the Company’s Class A common stock. The ESPP allows eligible employees to purchase shares of the Company’s Class A common stock through payroll deductions at a price equal to 85% of the lesser of the fair market value of the stock as of the first date or the ending date of each six month offering period. The 2014 Plan and the ESPP also provides for automatic annual increases in the number of shares reserved for future issuance. Employee retirement plan. The Company has a defined contribution retirement plan covering U.S. and other international full-time employees that provides for voluntary employee contributions from 1% to 100% of annual compensation, subject to a maximum limit allowed by Internal Revenue Service guidelines. The Company matches 100% of each employee’s contributions up to a maximum of 4% of the employee’s eligible compensation. The Company’s matching contributions to the plan were $5.5 million , $7.2 million and $5.5 million in 2017 , 2016 and 2015 , respectively. S tock options A summary of the Company’s stock option activity is as follows: Options outstanding Shares (in thousands) Weighted- average Weighted-average remaining contractual term (in years) Aggregate intrinsic value Outstanding at December 31, 2016 12,379 $ 12.17 5.97 $ 32,772 Granted 1,848 9.28 Exercised (1,329 ) 1.70 Forfeited/Cancelled (3,089 ) 18.15 Outstanding at December 31, 2017 9,809 $ 11.16 6.00 $ 19,971 Vested and expected to vest at December 31, 2017 9,786 $ 11.15 6.00 $ 19,971 Exercisable at December 31, 2017 8,154 $ 10.99 5.45 $ 19,971 The weighted average grant date fair value of all options granted and assumed were $4.06 , $4.84 and $18.40 per share in 2017 , 2016 and 2015 , respectively. The total fair value of all options vested was $19.5 million , $27.2 million and $26.9 million in 2017 , 2016 and 2015 , respectively. The aggregate intrinsic value of the stock options outstanding as of December 31, 2017 represents the value of the Company’s closing stock price on the last trading day of the year in excess of the exercise price multiplied by the number of options outstanding. Restricted stock units A summary of the Company’s RSU activity is as follows: Shares (in thousands) Weighted- average grant date fair value Non-vested shares at December 31, 2016 7,970 $ 18.08 Granted 8,740 9.40 Vested (3,862 ) 14.95 Forfeited (3,365 ) 16.62 Non-vested shares at December 31, 2017 9,483 $ 11.87 The weighted average grant date fair value of all RSUs granted were $9.40 , $12.10 and $44.00 per share in 2017 , 2016 and 2015 , respectively. The total fair value of all RSUs vested was $57.7 million , $49.5 million and $34.4 million in 2017 , 2016 and 2015 , respectively. In June 2014, the Company granted an award of 4.5 million RSUs covering shares of the Company’s Class B common stock to the Company’s CEO (CEO RSUs), which included 1.5 million RSUs that vested immediately upon grant and 3.0 million RSUs that were subject to both a market-based vesting condition and a three -year service-based vesting condition. The market-based condition was achieved in January 2015. Stock-based compensation expense related to the CEO RSUs was $0.6 million , $6.4 million and $29.4 million for 2017 , 2016 and 2015 , respectively. Employee stock purchase plan. In 2017 , 2016 and 2015 , the Company issued 934,359 , 668,107 and 436,924 shares under its ESPP at weighted average prices of $8.02 , $9.15 and $26.88 , respectively. Fair value disclosures. The fair value of stock options granted and purchases under the Company’s ESPP is estimated using the Black-Scholes option pricing model. Expected term of stock options granted was estimated based on the simplified method. Expected stock price volatility was estimated by taking the average of our historic volatility and the historical volatility for industry peers based on daily price observations over a period equivalent to the expected term. Risk-free interest rate was based on the yields of U.S. Treasury securities with maturities similar to the expected term. Dividend yield was zero as the Company does not have any history of, nor plans to make, dividend payments. The fair value of stock options granted was estimated as of the grant date using the following assumptions: Year ended December 31, 2017 2016 2015 Volatility 44%–49% 44%–45% 43%–54% Expected term (years) 5.3–5.8 5.2–6.1 5.5–7.0 Risk-free interest rate 1.8%–2.1% 1.2%–2.0% 1.6%–2.0% Dividend yield —% —% —% The fair value of stock purchase rights granted under the ESPP was estimated using the following assumptions: Year ended December 31, 2017 2016 2015 Volatility 33%–36% 43%–54% 39%–45% Expected term (years) 0.5 0.5 0.5 Risk-free interest rate 0.7%–1.2% 0.4%–0.5% 0.1%–0.2% Dividend yield —% —% —% Stock-based compensation expense. The following table summarizes stock-based compensation included in the consolidated statements of operations: Year ended December 31, (in thousands) 2017 2016 2015 Cost of revenue $ 1,935 $ 1,616 $ 1,492 Research and development 24,963 31,365 18,024 Sales and marketing 10,498 13,883 13,762 General and administrative 13,859 22,663 47,402 Total stock-based compensation expense $ 51,255 $ 69,527 $ 80,680 The income tax benefit related to stock-based compensation expense was zero for 2017 and 2016 , and $28.0 million for 2015 . There is no tax benefit due to a full valuation allowance for 2017 and 2016 on the Company’s U.S. net deferred tax assets (see Note 9 below). At December 31, 2017 , total unearned stock-based compensation of $97.3 million related to stock options, RSUs and ESPP shares is expected to be recognized over a weighted average period of 2.0 years.

Net loss per share

Net loss per share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net loss per share	Net income (loss) per share On April 12, 2017, the Company issued $175.0 million of 3.50% Convertible Senior Notes. The Notes mature on April 15, 2022, unless earlier repurchased or converted into shares of Class A common stock under certain circumstances as described further in Note 5, Financing Arrangements, above. The Notes are convertible into cash, shares of the Company’s Class A common stock, or a combination thereof, at the Company’s election. As the Company currently has the intent and ability to deliver cash up to the principal amount of the Notes subject to conversion, no shares associated with the Note conversion were included in the Company’s weighted-average number of common shares outstanding for any periods presented. While the Company has the intent and ability to settle any conversion in cash, the maximum number of shares issuable upon conversion of the Notes is 20.6 million shares of Class A common stock. Additionally, the calculation of weighted-average shares outstanding as of December 31, 2017 excludes approximately 6.6 million shares effectively repurchased and held in treasury stock on the consolidated balance sheet as a result of the Prepaid Forward transactions entered into in connection with the Note offering. The rights of the holders of Class A common stock and Class B common stock are identical, except with respect to voting and conversion. Each share of Class A common stock is entitled to one vote per share and each share of Class B common stock is entitled to ten votes per share. Each share of Class B common stock is convertible at any time at the option of the stockholder into one share of Class A common stock and has no expiration date. Each share of Class B common stock will convert automatically into one share of Class A common stock upon the date when the outstanding shares of Class B common stock represent less than 10% of the aggregate number of shares of common stock then outstanding. Class A common stock is not convertible into Class B common stock. The computation of the diluted net income (loss) per share of Class A common stock assumes the conversion of Class B common stock. The following table presents the calculations of basic and diluted net income (loss) per share: Year ended December 31, (in thousands, except per share data) 2017 2016 2015 Numerator: Net income (loss) $ (182,873 ) $ (419,003 ) $ 36,131 Denominator: Weighted-average common shares—basic for Class A and Class B common stock 138,056 139,425 134,595 Effect of dilutive stock-based awards — — 11,891 Weighted-average common shares—diluted for Class A and Class B common stock 138,056 139,425 146,486 Net income (loss) per share Basic $ (1.32 ) $ (3.01 ) $ 0.27 Diluted $ (1.32 ) $ (3.01 ) $ 0.25 The following potentially dilutive shares were not included in the calculation of diluted shares outstanding as the effect would have been anti-dilutive: Year ended December 31, (in thousands) 2017 2016 2015 Effect of anti-dilutive stock-based awards 18,994 21,000 2,681

Income taxes

Income taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income taxes	Income taxes Income (loss) before income taxes consisted of the following: Year ended December 31, (in thousands) 2017 2016 2015 Domestic $ (123,325 ) $ (200,595 ) $ 13,562 Foreign (53,062 ) (174,579 ) 39,023 $ (176,387 ) $ (375,174 ) $ 52,585 Income tax expense consisted of the following: Year ended December 31, (in thousands) 2017 2016 2015 Current Federal $ (1,857 ) $ (2,925 ) $ 18,548 State 240 (356 ) 3,007 Foreign 10,631 8,542 6,539 Total current 9,014 5,261 28,094 Deferred Federal (248 ) 37,573 (11,211 ) State — 4,436 (204 ) Foreign (2,280 ) (3,441 ) (225 ) Total deferred (2,528 ) 38,568 (11,640 ) Income tax expense $ 6,486 $ 43,829 $ 16,454 As of December 31, 2017 , $4.5 million of earnings had been indefinitely reinvested outside the U.S., primarily in active non-U.S. business operations. We do not intend to repatriate these earnings to fund U.S. operations and, accordingly, we do not provide for U.S. state income and foreign withholding tax on these earnings. See also TCJA discussion below. Year ended December 31, 2017 2016 2015 (dollars in thousands) $ % $ % $ % Reconciliation to statutory rate Tax at federal statutory rate $ (61,735 ) (35.0 )% $ (131,311 ) (35.0 )% $ 18,405 35.0 % Change in valuation allowance (38,016 ) (21.6 ) 101,878 27.2 8,555 16.3 DTA rate change impact due to TCJA 74,943 42.5 — — — — Impact of foreign operations 34,039 19.3 84,491 22.5 6,434 12.2 Stock-based compensation 12,001 6.8 15,718 4.2 2,390 4.5 State taxes, net of federal benefit (6,469 ) (3.7 ) (14,195 ) (3.8 ) 1,454 2.8 Tax credits (9,957 ) (5.6 ) (12,992 ) (3.5 ) (21,891 ) (41.6 ) Other 1,680 1.0 240 0.1 1,107 2.1 Income tax provision at effective tax rate $ 6,486 3.7 % $ 43,829 11.7 % $ 16,454 31.3 % The effective tax rate of 2017 resulted from a significant benefit on pre-tax book losses, offset by the valuation allowance on U.S. federal and state net deferred tax assets and by income taxes paid at lower rates in profitable foreign jurisdictions (primarily wholly owned subsidiaries in Europe). In addition, due to the U.S. enactment of the TCJA, U.S. deferred tax assets were revalued by $74.9 million at the statutory rate of 21% which will be effective January 1, 2018, with a corresponding valuation allowance adjustment. In addition, AMT credits of $0.2 million become refundable under the TCJA and $0.2 million of valuation allowance was released. The effective tax rate of 2016 resulted from a significant benefit on pre-tax book losses, offset by the establishment of a valuation allowance on all U.S. federal and state net deferred tax assets and by income taxes paid at lower rates in profitable foreign jurisdictions (primarily wholly owned subsidiaries in Europe). Overall, the provision for income taxes in each period has differed from the tax computed at U.S. federal statutory tax rates due to change in valuation allowance, the effect of non-U.S. operations, deductible and non-deductible stock-based compensation expense, states taxes, federal research and development tax credits, and other adjustments. The lower effective tax rates of 2016 compared to 2015 resulted from a significant benefit on pre-tax book losses, offset by the establishment of a valuation allowance on all U.S. federal and state net deferred tax assets and by income taxes paid at lower rates in profitable foreign jurisdictions (primarily wholly owned subsidiaries in Europe). The provision for income taxes in each period has differed from the tax computed at U.S. federal statutory tax rates due to change in valuation allowance, the effect of non-U.S. operations, deductible and non-deductible stock-based compensation expense, states taxes, federal research and development tax credits, and other adjustments. Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company’s deferred tax assets and liabilities were as follows: Year ended December 31, (in thousands) 2017 2016 Deferred tax assets: Net operating loss carryforwards $ 113,378 $ 30,193 Tax credit carryforwards 66,983 22,341 Stock-based compensation 13,055 26,656 Allowance for returns 5,452 6,336 Intangible assets 770 — Accruals and reserves 18,981 26,587 Total deferred tax assets 218,619 112,113 Valuation allowance (217,884 ) (110,433 ) Total deferred tax assets, net of valuation allowance 735 1,680 Deferred tax liabilities: Depreciation and amortization (292 ) (1,714 ) Intangible assets — (2,540 ) Total deferred tax liabilities (292 ) (4,254 ) Net deferred tax assets (liabilities) $ 443 $ (2,574 ) Recognition of deferred tax assets is appropriate when realization of such assets is more likely than not. Based upon the weight of available evidence, the Company believes it is not more likely than not that the U.S. deferred tax assets will be realized. Accordingly, a valuation allowance has been established and maintained against U.S. deferred tax assets. The foreign deferred tax assets in each jurisdiction are minimal and are supported by taxable income or in the case of acquired companies, by the future reversal of deferred tax liabilities. It is more likely than not that the Company’s foreign deferred tax assets will be realized and thus, no valuation allowance is required on foreign deferred tax assets. The Company will continue to assess the realizability of the deferred tax assets in each of the applicable jurisdictions going forward. The Company’s valuation allowance increased by $107.5 million to $217.9 million as of December 31, 2017 , primarily due to the impact of the ASU 2016-09 adoption that resulted in an increase in U.S. deferred tax assets of $163.0 million and current year movement on U.S. deferred tax assets of $36.9 million , offset by a decrease due to $17.5 million attributable to the debt discount on convertible debt, and a $74.9 million decrease due to the change in future tax rate under the enacted TCJA on December 22, 2017. As of December 31, 2016 , the Company had established a valuation allowance of $110.4 million on all U.S. federal and state deferred tax assets. As of December 31, 2017 , the Company’s federal, California and other state net operating loss carryforwards for income tax purposes were $456.1 million , $210.3 million and $233.7 million , net of reserves, respectively and federal and California state tax credit carryforwards were $39.6 million and $34.4 million , net of reserves, respectively. If not utilized, federal loss, federal credit and California loss carryforwards will begin to expire from 2030 to 2037, while other state loss carryforwards will begin to expire from 2019 to 2037. California tax credits may be carried forward indefinitely. Under the provisions of §382 of the Internal Revenue Code, a change of control may impose an annual limitation on the amount of the Company’s net operating loss and tax credit carryforwards that can be used to reduce future tax liabilities. Of the Company’s total $456.1 million federal net operating loss carryforwards, approximately $8.1 million was from one of our 2016 acquisitions. These acquired tax attributes are subject to an annual limitation of $1.7 million per year for federal purposes and will begin to expire in the year 2034, if not utilized. Uncertain income tax positions. The Company had gross unrecognized tax benefits of $58.6 million , $56.9 million and $36.3 million , as of December 31, 2017 , 2016 and 2015 , respectively. For fiscal 2017 , 2016 and 2015 , total unrecognized income tax benefits in the amount of $19.8 million , $24.1 million and $31.0 million , respectively, if recognized, would reduce income tax expense after considering the impact of the change in valuation allowance in the U.S. A material portion of our gross unrecognized tax benefits, if recognized, would increase the Company’s net operating loss carryforward, which would be offset by a full valuation allowance based on present circumstances. These unrecognized tax benefits relate primarily to unresolved matters with taxing authorities regarding the Company’s transfer pricing positions and tax positions based on the Company’s interpretation of certain U.S. trial and appellate court decisions, which remain subject to appeal and therefore could be overturned in future periods. Management believes events that could occur in the next 12 months and cause a material change in unrecognized tax benefits include, but are not limited to, the completion of examinations by the U.S. or foreign taxing authorities and the expiration of statute of limitations on the Company’s tax returns. Although the completion, settlement and closure of any audits is uncertain, it is reasonably possible based on the receipt of the Joint Committee approval of the federal claimed income tax refund relating to the carryback of 2014 and 2015 net operating losses on December 18, 2017, and the IRS Closing Agreement received on January 24, 2018, that over the next twelve-month period, our unrecognized tax benefits as of December 31, 2017 , will decrease in the range of $15.0 million to $20.0 million , of which approximately $2.0 million to $3.0 million benefit would impact our effective tax rate. Such reduction is due to the resolution of certain issues, primarily related to transfer pricing and the R&D credit, raised in connection with our federal examination. Thus, we believe that that the total amount of unrecognized tax benefits will decrease within the next 12 months. However, for all other jurisdictions, given the number of years remaining that are subject to examination, the range of the reasonably possible change cannot be estimated reliably. A reconciliation of the beginning and ending amount of the unrecognized income tax benefits are as follows: Year ended December 31, (in thousands) 2017 2016 2015 Gross balance at January 1 $ 56,909 $ 36,273 $ 16,558 Gross increase related to current year tax positions 20,002 20,594 19,948 Gross decrease related to tax rate change for current year tax positions (2,299 ) — — Gross increase related to prior year tax positions — 130 108 Gross decrease related to prior year tax positions (3,927 ) (88 ) (341 ) Gross decrease related to tax rate change for prior year tax positions (12,101 ) — — $ 58,584 $ 56,909 $ 36,273 Due to the U.S. enactment of the TCJA, U.S. unrecognized income tax benefits that reduce federal tax attributes are revalued at the statutory rate of 21% . Total gross decreases to unrecognized tax benefits were $14.4 million relating to the change in tax rates from 35% to 21% . The Company’s policy is to account for interest and penalties related to income tax liabilities within the provision for income taxes. The balances of accrued interest and penalties recorded in the balance sheets and provision were not material for any period presented. The Company files income tax returns in U.S. and non-U.S. jurisdictions. The Company is subject to federal, state and foreign income tax examinations for calendar tax years ending 2012 through 2016. The tax authorities could choose to audit the tax years beyond the statute of limitation period due to tax attribute carryforwards from prior years, making adjustments only to carryforward attributes. The Company has been under examination by the Internal Revenue Service for the 2012 through 2015 tax years. IRS audit fieldwork has been completed and the claimed income tax refund of approximately $32.9 million relating to the carryback of 2014 and 2015 net operating losses was approved by the Congressional Joint Committee on Taxation (JCT) on December 18, 2017. See also Note 14 Subsequent Events for additional information. U.S. Tax Reform. The Tax Cuts and Job Act (TCJA) of 2017, enacted on December 22, 2017, contains significant changes to U.S. tax law, including lowering the U.S. corporate income tax rate to 21%, implementing a territorial tax system, and imposing a one-time tax on deemed repatriated earnings of foreign subsidiaries. The TCJA reduces the U.S. statutory tax rate from 35% to 21% , effective January 1, 2018. During the three months ended December 31, 2017, the Company recorded a $74.9 million tax expense representing the detriment of remeasuring its U.S. deferred tax liabilities at the lower 21% statutory tax rate, as well as a corresponding full valuation allowance for the same amount resulting in no impact to our Statement of Operations. The TCJA also implements a territorial tax system. Under the territorial tax system, in general, the Company’s foreign earnings will no longer be subject to tax in the U.S. As part of transitioning to the territorial tax system the TCJA includes a mandatory deemed repatriation of all undistributed foreign earnings that are subject to a U.S. income tax. The Company estimates that the deemed repatriation will not result in any additional U.S. income tax. This preliminary estimate may be impacted by a number of additional considerations, including, but not limited to, the issuance of final regulations and the Company's ongoing analysis of the new law. As of December 31, 2017 , the Company has approximately $4.5 million of undistributed earnings for certain non-U.S. subsidiaries that have been indefinitely reinvested outside the U.S. These undistributed earnings do not result in a one-time deemed repatriation tax due to our overall accumulated foreign deficit, however these earnings could be subject to additional foreign and state income taxes if they are repatriated. The Company has historically asserted its intent to reinvest these earnings in foreign operations indefinitely and continues to do so. We do not intend to repatriate these earnings to fund U.S. operations and, accordingly, we do not provide for U.S. state income and foreign withholding tax on these earnings. While the TJCA provides for a territorial tax system, beginning in 2018, it includes two new U.S. tax base erosion provisions, the global intangible low-taxed income (GILTI) provisions and the base-erosion and anti-abuse tax (BEAT) provisions. The GILTI provisions require the Company to include in its U.S. income tax return foreign subsidiary earnings in excess of an allowable return on the foreign subsidiary’s tangible assets. The Company does not expect that this GILTI income inclusion will result in significant U.S. tax beginning in 2018. The BEAT provisions in the TCJA eliminates the deduction of certain base-erosion payments made to related foreign corporations and impose a minimum tax if greater than regular tax. The Company does not expect that the BEAT provision will result in significant U.S. tax beginning in 2018. In addition, the Company intends to account for the GILTI taxes in the period in which it is incurred, and therefore has not provided any deferred tax impacts of GILTI in its consolidated financial statements for the year ended December 31, 2017. On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118 (SAB 118) to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the TCJA. The Company has recognized the provisional tax impacts related to deemed repatriated earnings and the revaluation of deferred tax assets and liabilities to the extent needed and included these amounts in its consolidated financial statements for the year ended December 31, 2017 . The ultimate impact may differ from these provisional amounts, possibly materially, due to, among other things, additional analysis, changes in interpretations and assumptions the Company has made, additional regulatory guidance that may be issued, and actions the Company may take as a result of the TCJA. The accounting is expected to be complete when the 2017 U.S. corporate income tax return is filed in 2018.

Related party transactions

Related party transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related party transactions	Related party transactions The Company incurs costs for Company-related chartered aircraft fees for the use of the CEO’s private plane. The Company recorded expense of $0.1 million , $0.5 million and $0.7 million in 2017 , 2016 and 2015 , respectively. As of December 31, 2017 and 2016 , the Company had zero accounts payable associated with these aircraft fees. In 2013, the Company entered into a three -year agreement, which was amended in July 2016 to continue through the end of 2016, with a company affiliated with the son of one of the then members of the Company’s board of directors to acquire certain naming rights to a kart racing facility. As consideration for these naming rights, the Company paid $0.6 million over the three year period. As of December 31, 2016 , the Company has recorded cumulative expense of $0.6 million , and has also provided 100 GoPro cameras at no cost each year. As of December 31, 2016 and 2015 , the Company had no accounts payable associated with this agreement. In 2016, the Company obtained services from a vendor whose CEO is also one of the members of the Company’s board of directors. The Company recorded expense of zero and $0.4 million in 2017 and 2016 , respectively. As of December 31, 2017 and 2016 , the Company had accounts payable associated with this vendor of zero and $0.3 million , respectively. The Company has agreements for certain contract manufacturing and engineering services with a vendor affiliated with one of the Company’s investors. The Company made payments of zero to this vendor in 2017 and 2016 and $0.2 million in 2015 . As of December 31, 2017 and 2016 , the Company had no accounts payable associated with this vendor. See Note 6 and 7 above for information regarding CEO RSUs and Class B common stock contributed by the CEO back to the Company.

Commitments, contingencies and

Commitments, contingencies and guarantees	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments, contingencies and guarantees	Commitments, contingencies and guarantees (in thousands) Total 2018 2019 2020 2021 2022 Thereafter Operating leases (1) $ 128,228 $ 22,177 $ 15,056 $ 18,244 $ 17,817 $ 16,693 $ 38,241 Sponsorship commitments (2) 7,256 4,487 2,769 — — — — Other contractual commitments (3) 2,766 2,044 722 — — — — Long-term debt (4) 175,000 — — — — 175,000 — Total contractual cash obligations $ 313,250 $ 28,708 $ 18,547 $ 18,244 $ 17,817 $ 191,693 $ 38,241 (1) The Company leases its facilities under long-term operating leases, which expire at various dates through 2027. (2) The Company enters into multi-year sponsorship agreements with event organizers, resorts and athletes as part of its marketing efforts. (3) The Company enters into other contractual commitments, including software licenses related to the Company’s financial and IT systems which require payments over several years. (4) The Company's convertible senior notes are due April 2022. Refer to Note 5 Financing Arrangements. In 2017 and 2016 , the Company entered into sub-lease agreements for its office facilities that decreased the Company’s total future minimum lease payments by sub-lease rentals of approximately $4.3 million which approximates the corresponding remaining lease rentals. Rent expense was $19.1 million , $19.8 million and $12.2 million for 2017 , 2016 and 2015 , respectively. Legal proceedings. From time to time, the Company is involved in legal proceedings in the ordinary course of business. Due to inherent uncertainties of litigation, the Company cannot accurately predict the ultimate outcome of these matters. The Company is unable at this time to determine whether the outcome of the litigation would have a material impact on the results of operations, financial condition or cash flows of the Company. 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. It is not possible to determine the maximum potential amount under these indemnification agreements due to the Company’s limited history with indemnification claims and the unique facts and circumstances involved in each particular agreement. As of December 31, 2017 , the Company has not paid any claims nor has it 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.

Concentrations of risk and geog

Concentrations of risk and geographic information	12 Months Ended
	Dec. 31, 2017
Risks and Uncertainties [Abstract]
Concentrations of risk and segment information	Concentrations of risk and geographic information Customer concentration. Financial instruments, which potentially subject the Company to concentrations of credit risk, consist principally of trade receivables. The Company believes that credit risk for accounts receivable is mitigated by the Company’s credit evaluation process, relatively short collection terms and dispersion of its customer base. The Company generally does not require collateral and losses on trade receivables have historically been within management’s expectations. Customers who represented 10% or more of the Company’s net accounts receivable balance were as follows: December 31, 2017 December 31, 2016 Customer A 16% 15% Customer B 32% 27% Customer C 12% * Customer D 11% * The following table summarizes the Company’s accounts receivables sold, without recourse, and factoring fees paid: Year ended December 31, (in thousands) 2017 2016 2015 Accounts receivable sold $ 178,300 $ 167,769 $ 194,223 Factoring fees 1,630 1,266 1,566 Customers who represented 10% or more of the Company’s total revenue were as follows: Year ended December 31, 2017 2016 2015 Customer A 15% 17% 14% Customer B * 11% 12% * Less than 10% of total revenue for the period indicated Supplier concentration. The Company relies on third parties for the supply and manufacture of its products, some of which are sole-source suppliers. The Company believes that outsourcing manufacturing enables greater scale and flexibility. As demand and product lines change, the Company periodically evaluates the need and advisability of adding manufacturers to support its operations. In instances where a supply and manufacture agreement does not exist or suppliers fail to perform their obligations, the Company may be unable to find alternative suppliers or satisfactorily deliver its products to its customers on time, if at all. The Company also relies on third parties with whom it outsources supply chain activities related to inventory warehousing, order fulfillment, distribution and other direct sales logistics . Geographic information Revenue by geographic region, based on ship-to destinations, was as follows: Year ended December 31, (in thousands) 2017 2016 2015 Americas $ 591,879 $ 619,784 $ 868,772 Europe, Middle East and Africa (EMEA) 334,872 366,352 535,260 Asia and Pacific (APAC) 252,990 199,345 215,939 Total revenue $ 1,179,741 $ 1,185,481 $ 1,619,971 Revenue in the United States, which is included in the Americas geographic region, was $528.7 million , $554.9 million and $769.2 million for 2017 , 2016 and 2015 , respectively. No other individual country exceeded 10% of total revenue for any period presented. The Company does not disclose revenue by product category as it does not track sales incentives and other revenue adjustments by product category to report such data. As of December 31, 2017 and 2016 , long-lived assets, which represent gross property and equipment, located outside the United States, primarily in Hong Kong and China, were $79.7 million and $76.6 million , respectively.

Restructuring charges

Restructuring charges	12 Months Ended
	Dec. 31, 2017
Restructuring and Related Activities [Abstract]
Restructuring charges	Restructuring charges Restructuring charges for each period were as follows: Twelve months ended (in thousands) December 31, 2017 December 31, 2016 Cost of revenue $ 634 $ 497 Research and development 10,092 17,197 Sales and marketing 7,047 12,064 General and administrative 2,519 13,331 Total restructuring charges $ 20,292 $ 43,089 First quarter 2017 restructuring On March 15, 2017, the Company approved a restructuring plan to further reduce future operating expenses and further align resources around its long-term business strategy. The restructuring provided for a reduction of the Company's global workforce by approximately 270 positions, and the consolidation of certain leased office facilities. Under the first quarter 2017 restructuring plan, the Company recorded restructuring charges of $17.0 million , including $10.3 million related to severance, and $6.7 million related to accelerated depreciation and other charges. The actions associated with the first quarter 2017 restructuring plan were substantially completed by the fourth quarter of 2017. While the Company anticipates that any additional charges related to this restructuring will be immaterial, actual results may differ from current estimates as it relates to the consolidation of certain leased office facilities. The following table provides a summary of the Company’s restructuring activities during 2017 and the related liabilities recorded in accrued liabilities on the consolidated balance sheet. (in thousands) Severance Other Total Restructuring liability as of December 31, 2016 $ — $ — $ — Restructuring charges 10,312 6,654 16,966 Cash paid (9,509 ) (151 ) (9,660 ) Non-cash reductions (803 ) (2,953 ) (3,756 ) Restructuring liability as of December 31, 2017 $ — $ 3,550 $ 3,550 Fourth quarter 2016 restructuring On November 29, 2016, the Company approved a restructuring plan to reduce future operating expenses. The restructuring provided for a reduction of the Company’s global workforce of approximately 15% , the closure of the Company’s entertainment group to concentrate on its core business and the consolidation of certain leased office facilities. Under the fourth quarter 2016 restructuring plan, the Company recorded restructuring charges of $40.7 million , including $3.2 million related to severance and facilities contract terminations during 2017. The actions associated with the fourth quarter 2016 restructuring plan were completed by March 31, 2017, with only small incremental charges recorded through December 31, 2017. The following table provides a summary of the Company’s restructuring activities during 2017 and the related liabilities recorded in accrued liabilities on the consolidated balance sheet. (in thousands) Severance Other Total Restructuring liability as of December 31, 2016 $ 9,660 $ 879 $ 10,539 Restructuring charges 2,134 1,055 3,189 Cash paid (11,411 ) (1,884 ) (13,295 ) Non-cash reductions 17 — 17 Restructuring liability as of December 31, 2017 $ 400 $ 50 $ 450 First quarter 2016 restructuring On January 12, 2016, the Company approved a restructuring plan that provided for a reduction in the Company’s global workforce of approximately 7% . Under the first quarter 2016 restructuring plan, the Company recorded restructuring charges of $6.5 million in the first quarter of 2016, which primarily included cash-based severance costs. The Company completed this plan at the end of the first quarter of 2016 and all costs have been paid. No charges were recorded in periods after March 31, 2016.

Valuation and Qualifying Accoun

Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2017
Valuation and Qualifying Accounts [Abstract]
Schedule of Valuation and Qualifying Accounts Disclosure [Text Block]	VALUATION AND QUALIFYING ACCOUNTS For the years ended December 31, 2017, 2016 and 2015 (in thousands) Balance at Beginning of Year Charges to Revenue Charges to Expense Charges to Other Accounts - Equity Deductions/Write-offs Balance at End of Year Allowance for doubtful accounts receivable: Year ended December 31, 2017 $ 1,281 $ — $ (263 ) $ — $ (268 ) $ 750 Year ended December 31, 2016 1,400 — 40 — (159 ) 1,281 Year ended December 31, 2015 1,250 — 682 — (532 ) 1,400 Allowance for sales returns: Year ended December 31, 2017 $ 20,038 $ 55,274 $ (48,554 ) $ — $ — $ 26,758 Year ended December 31, 2016 26,280 35,136 (41,378 ) — — 20,038 Year ended December 31, 2015 25,747 48,182 (47,649 ) — — 26,280 Valuation allowance for deferred tax assets: Year ended December 31, 2017 $ 110,433 $ — $ (38,016 ) $ 145,467 $ — $ 217,884 Year ended December 31, 2016 8,555 — 101,878 — — 110,433 Year ended December 31, 2015 — — 8,555 — — 8,555

Subsequent Events (Notes)

Subsequent Events (Notes)	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events [Text Block]	Subsequent events On January 2, 2018, the Company approved a restructuring plan to further reduce future operating expense and better align resources around its long-term business strategy. The restructuring provided for a reduction of the Company's global workforce of approximately 21% , the closure of the Company's aerial group and the consolidation of certain leased office facilities. The Company estimates that it will incur total aggregate charges of approximately $23 million to $33 million for the restructuring. The Company expects actions associated with the restructuring will be substantially completed in the first quarter of 2018. The Company has been under examination by the Internal Revenue Service for the 2012 through 2015 tax years. The IRS audit fieldwork has been completed and the claimed income tax refund relating to the carryback of 2014 and 2015 net operating losses was approved by the Congressional Joint Committee on Taxation (JCT) on December 18, 2017. The Closing Agreement was received on January 24, 2018. The Company received an income tax refund of approximately $32.9 million , net of IRS adjustments, in February 2018. The Company will also recognize an income tax benefit of approximately $2.0 million to $3.0 million in the first quarter of 2018.

Summary of business and signi22

Summary of business and significant accounting policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation.
Principles of consolidation	Principles of consolidation. These consolidated financial statements include all the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
Use of estimates	Use of estimates. The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the amounts reported and disclosed in the Company’s consolidated financial statements and accompanying notes. Significant estimates and assumptions made by management include those related to revenue recognition (including sales returns, implied post contract support, price protection and other sales incentives), stock-based compensation, inventory valuation, product warranty liabilities, the valuation and useful lives of long-lived assets (property and equipment, intangible assets and goodwill) and income taxes. The Company bases its estimates and assumptions on historical experience and on various other factors that it believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results could differ materially from management’s estimates. To the extent there are material differences between the estimates and the actual results, future results of operations could be affected.
Comprehensive income (loss)	Comprehensive income (loss). For all periods presented, comprehensive income (loss) approximated net income (loss). Therefore, the consolidated statements of comprehensive income (loss) have been omitted
Prior period reclassifications	Prior period reclassifications. Reclassifications of certain prior period amounts in the consolidated financial statements have been made to conform to the current period presentation.
Cash equivalents and marketable securities	Cash equivalents and marketable securities. Cash equivalents primarily consist of investments in money market funds with maturities of three months or less from the date of purchase. Marketable securities consist of commercial paper, U.S. agency securities, and corporate debt securities, and are classified as available-for-sale securities. The Company views these securities as available to support current operations and it has classified all available-for-sale securities as current assets. Available-for-sale securities are carried at fair value with unrealized gains and losses, if any, included in stockholders’ equity. Unrealized losses are charged against other income (expense), net, for declines in fair value below the cost of an individual investment that is deemed to be other than temporary. The Company has not identified any marketable securities as other-than-temporarily impaired for the periods presented. The cost of securities sold is based upon a specific identification method.
Accounts receivable and allowance for doubtful accounts	Accounts receivable and allowance for doubtful accounts. Accounts receivable are stated at invoice value less estimated allowances for returns and doubtful accounts. Allowances are recorded based on the Company’s assessment of various factors, such as: historical experience, credit quality of its customers, age of the accounts receivable balances, geographic related risks, economic conditions and other factors that may affect a customer’s ability to pay. The allowance for doubtful accounts as of December 31, 2017 and 2016 was $0.8 million and $1.3 million , respectively.
Inventory	Inventory. Inventory consists of finished goods and component parts, which are purchased directly from suppliers or from contract manufacturers. Inventory is stated at the lower of cost or net realizable value on a first-in, first-out basis. The Company writes down its inventory for estimated obsolescence or excess inventory equal to the difference between the cost of inventory and estimated market value. The Company’s assessment of market value is based upon assumptions around market conditions and estimated future demand for its products within a specified time horizon, generally 12 months. Adjustments to reduce inventory to net realizable value are recognized in cost of revenue.
Point of purchase (POP) displays	Point of purchase (POP) displays. The Company provides retailers with POP displays, generally free of charge, in order to facilitate the marketing of the Company’s products within retail stores. The POP displays contain a display that broadcasts video images taken by GoPro cameras with product placement available for cameras and accessories. POP display costs, less any fees charged, are capitalized as long-term assets and charged to sales and marketing expense over the expected period of benefit, which generally ranges from 24 to 36 months . Cash outflows and amortization related to POP displays are classified as operating activities in the consolidated statement of cash flows. Amortization was $19.2 million , $19.6 million and $16.8 million in 2017 , 2016 and 2015 , respectively.
Property and equipment, net	Property and equipment, net. Property and equipment are stated at cost and are depreciated using the straight-line method over the estimated useful life of the assets, ranging from one to eleven years. Leasehold improvements are amortized over the shorter of the lease term or their expected useful life. Property and equipment pending installation, configuration or qualification are classified as construction in progress. Costs of maintenance and repairs that do not improve or extend the lives of the respective assets are expensed as incurred.
Fair value measurements	Fair value measurements. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the reporting date. The Company estimates and categorizes the fair value of its financial assets by applying the following hierarchy: Level 1 Valuations based on quoted prices in active markets for identical assets or liabilities that the Company has the ability to directly access. Level 2 Valuations based on quoted prices for similar assets or liabilities; valuations for interest-bearing securities based on non-daily quoted prices in active markets; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable data for substantially the full term of the assets or liabilities. Level 3 Valuations based on inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The fair value of Level 2 financial instruments is obtained from an independent pricing service, which may use quoted market prices for identical or comparable instruments or model driven valuations using observable market data or inputs corroborated by observable market data.
Leases	Leases. The Company leases its office space and facilities under cancelable and non-cancelable operating leases. For leases that contain rent escalation or rent concession provisions, the Company recognizes rent expense on a straight-line basis over the term of the lease. The Company does not assume renewals in its determination of the lease term unless the renewals are deemed to be reasonably assured at lease inception.
Goodwill and other intangible assets	Goodwill and other intangible assets. Goodwill represents the excess of the purchase price over the fair value of the net assets acquired in a business combination. Acquired intangible assets other than goodwill are amortized over their useful lives unless the lives are determined to be indefinite. For intangible assets acquired in a business combination, the estimated fair values of the assets received are used to establish their recorded values. Valuation approaches consistent with the market approach, income approach and/or cost approach are used to measure fair value.
Impairment of goodwill	Impairment of goodwill and long-lived assets. The Company performs an annual assessment of its goodwill during the fourth quarter of each calendar year or more frequently if indicators of potential impairment exist, such as an adverse change in business climate or a decline in the overall industry demand, that would indicate it is more likely than not that the fair value of its single reporting unit is less than its carrying value. There was no impairment of goodwill recorded for any periods presented. For annual impairment testing in 2017 , the Company performed a quantitative analysis and determined the fair value of its single reporting unit exceeded the carrying value. Other indefinite-lived intangible assets are assessed for impairment at least annually. If their carrying value exceeds the estimated fair value, the difference is recorded as an impairment. See Note 4 for information regarding impairment charges recorded for indefinite-lived intangible assets. Long-lived assets, such as property and equipment and intangible assets subject to amortization, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset group may not be recoverable. Recoverability of assets to be held and used is measured by comparing the carrying amount to the estimated future undiscounted cash flows expected to be generated by the asset group. If it is determined that an asset group is not recoverable, an impairment charge is recognized for the amount by which the carrying amount of the asset group exceeds its fair value. There was no material impairment of long-lived assets for any periods presented.
Warranty	Warranty. The Company records a liability for estimated product warranty costs at the time product revenue is recognized. The Company’s standard warranty obligation to its end-users generally provides a 12 -month warranty coverage on all of its products except in the European Union where the Company provides a 2 -year warranty. An extended warranty is also available for a fee. The Company’s estimate of costs to service its warranty obligations is based on its historical experience of repair and replacement of the associated products and expectations of future conditions. The warranty obligation is affected by product failure rates and the related use of materials, labor costs and freight incurred in correcting any product failure.
Revenue recognition	Revenue recognition. Revenue is primarily comprised of product revenue, net of returns and sales incentives. The Company derives substantially all of its revenue from the sale of cameras, drones, mounts and accessories and the related implied post contract support (PCS). The Company recognizes revenue when persuasive evidence of an arrangement exists, delivery has occurred, the sales price is fixed or determinable, and collectability is reasonably assured. For most of the Company’s revenue, these criteria are met at the time the product is shipped. For customers who purchase products directly from the Company’s website, revenue is deferred until delivery to the customer’s address because the Company retains a portion of the risk of loss on these sales during transit. The Company's standard terms and conditions of sale for non-web based sales do not allow for product returns other than under warranty. However, the Company grants limited rights to return product for certain large retailers and distributors. Estimates of expected future product returns are recognized at the time of sale based on analyses of historical return trends by customer class. Upon recognition, the Company reduces revenue and cost of sales for the estimated returns. Return trends are influenced by product life cycles, new product introductions, market acceptance of products, product sell-through, the type of customer, seasonality and other factors. Return rates may fluctuate over time, but are sufficiently predictable to allow the Company to estimate expected future product returns. The Company’s camera sales are multiple element arrangements that generally include the following three separate units of accounting: a) a hardware component (camera, drone and/or accessories) and the embedded firmware essential to the functionality of the hardware component delivered at the time of sale, b) the implicit right to the Company's downloadable free apps and software solutions (GoPro and Quik apps), and c) the implied right for the customer to receive PCS. PCS includes the right to receive, on a when and if available basis, future unspecified firmware upgrades and features as well as bug fixes, and email and telephone support. The Company accounts for each element separately and allocates revenue based on its best estimate of the selling price (BESP). The Company’s process for determining BESP considers multiple factors that may vary over time depending upon the unique facts and circumstances related to each deliverable, including: the level of support provided to customers, estimated costs to provide the Company’s support, the amount of time and cost that is allocated to the Company’s efforts to develop the undelivered elements, and market trends in the pricing for similar offerings. Revenue allocated to the delivered hardware, related essential software and free software is recognized at the time of sale provided the conditions for recognition of revenue have been met. Revenue allocated to PCS is deferred and recognized on a straight-line basis over the estimated term of the support period, which is estimated to be 15 months based on historical experience. Deferred revenue also includes amounts related to the Company’s GoPro Care and GoPro Plus fee-based service offerings.
Sales incentives	Sales incentives. The Company offers sales incentives through various programs, including cooperative advertising, marketing development funds and other incentives. Sales incentives are recorded as a reduction to revenue in the period the incentives are offered to the Company’s customers or the related revenue is recognized, whichever is later. In addition, the Company offers price protection discounts to certain customers, which are recorded as a reduction of revenue at the date of sale.
Shipping costs	Shipping costs. Amounts billed to customers for shipping and handling are classified as revenue and the Company’s related shipping and handling costs incurred are classified as cost of revenue.
Sales taxes	Sales taxes. Sales taxes collected from customers and remitted to respective governmental authorities are recorded as liabilities and are not included in revenue.
Advertising costs	Advertising costs. Advertising costs consist of costs associated with print, television and e-commerce media advertisements and are expensed as incurred. The Company incurs promotional expenses resulting from payments under event, resort and athlete sponsorship contracts. These sponsorship arrangements are considered to be executory contracts and, as such, the costs are expensed as performance under the contract is received. The costs associated with preparation of sponsorship activities, including the supply of GoPro products, media team support, and activation fees are expensed as incurred. Prepayments made under sponsorship agreements are included in prepaid expenses or other long-term assets depending on the period to which the prepayment applies. Advertising costs were $61.3 million , $106.0 million and $64.7 million in 2017 , 2016 and 2015 , respectively.
Stock-based compensation	Stock-based compensation. The Company accounts for stock-based compensation in accordance with accounting guidance that requires all stock-based awards granted to employees and directors to be measured at fair value and recognized as an expense. The Company primarily issues restricted stock units and accounts for forfeitures as they occur. For service-based awards, stock-based compensation is recognized on a straight-line basis over the requisite service period. For performance and market-based awards which also require a service period, the Company uses graded vesting over the longer of the derived service period or when the performance or market condition is satisfied.
Foreign currency	Foreign currency. The U.S. dollar is the functional currency of the Company’s foreign subsidiaries. The Company remeasures monetary assets or liabilities denominated in currencies other than the U.S. dollar using exchange rates prevailing on the balance sheet date, and non-monetary assets and liabilities at historical rates. Foreign currency remeasurement and transaction gains and losses are included in other income (expense), net and have not been material for any periods presented.
Income Taxes	Income taxes. The Company utilizes the asset and liability method for computing its income tax provision, under which deferred tax assets and liabilities are recognized for the expected future consequences of temporary differences between the financial reporting and tax bases of assets and liabilities using enacted tax rates. Management makes estimates, assumptions and judgments to determine the Company’s provision for income taxes, deferred tax assets and liabilities, and any valuation losses recorded against deferred tax assets. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent the Company believes recovery is not likely, establishes a valuation allowance. The Company recognizes the tax benefit from an uncertain tax position only if it is more likely than not the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The tax benefits recognized from such positions are then measured based on the largest benefit that has a greater than 50% likelihood of being realized upon settlement. Interest and penalties related to unrecognized tax benefits are recognized within income tax expense.
Segment Reporting, Policy [Policy Text Block]	Segment information. The Company operates as one operating segment as it only reports financial information on an aggregate and consolidated basis to its CEO, who is the Company’s chief operating decision maker.
Recent accounting pronouncements	Recent accounting standards Standard Description Date of adoption Effect on the financial statements or other significant matters Standards that were adopted Stock Compensation This standard simplifies certain aspects of the accounting for share-based payment transactions, including income taxes, classification of awards and classification on the statement of cash flows. The new guidance also allows an entity to make a policy election to account for forfeitures as they occur. January 1, 2017 Adoption of the standard resulted in the recognition of previously unrecognized excess tax benefits using the modified retrospective method. The Company recorded an increase to U.S. deferred tax assets of $179 million which was recorded directly against the accumulated deficit. The increased deferred tax asset allowed for an offset against long-term income tax payable of $16 million. A full valuation allowance was provided on the remaining U.S. deferred tax asset of $163 million, which was also recorded against the accumulated deficit. The net impact to equity was a decrease in the accumulated deficit of approximately $16 million. The Company elected to apply the change in presentation to the statements of cash flows prospectively and elected to account for forfeitures as they occur. Standards not yet adopted Revenue from Contracts with Customers ASU No. 2014-09, 2015-14, 2016-08, 2016-10 and 2016-12 (Topic 606) The updated revenue standard establishes principles for recognizing revenue and develops a common revenue standard for all industries. Under the new model, recognition of revenue occurs when a customer obtains control of promised goods or services in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The new standard requires that entities disclose the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Early adoption is permitted, but not earlier than the first quarter of 2017. The retrospective or cumulative effect transition method is permitted. January 1, 2018 The Company completed an analysis of the impact of the standard on its sales contract portfolio by reviewing its current accounting policies and practices to identify differences that would result from applying the requirements of the new standard to its sales contracts. The Company’s analysis of its contracts under the new standard supports the recognition of its product revenue at the time product is shipped, consistent with its current revenue policy. As a result of the adoption of the new guidance, certain sales incentives will need to be estimated as variable consideration at the time product is shipped and included as a reduction to the transaction price. This will result in a reduction of revenue being recorded earlier than under the existing guidance. Additionally, for customers who purchase products directly from the Company's website, the new standard provides for a policy election whereby the Company will record revenue when the related product is shipped. This will result in recognition of revenue earlier than under existing guidance, under which the Company recognizes revenue upon delivery to the customer. The Company expects the net impact of ASU 2014-09 to be less than $5 million as a reduction to retained earnings. The Company will adopt the standard on a modified retrospective basis. Leases ASU No. 2016-02(Topic 842) This standard requires lessees to put most leases on their balance sheets but recognize the expenses on their income statements in a manner similar to current practice. Lessees would recognize a right-to-use asset and lease liability for all leases with terms of more than 12 months. The new standard should be applied on a modified retrospective basis. January 1, 2019 Although the Company is currently evaluating the impact that the adoption of this standard will have on its consolidated financial statements and related disclosures, the Company currently expects that most of its operating lease commitments will be subject to the new standard and recognized as operating lease liabilities and right-of-use assets upon adoption. Income Taxes ASU No. 2016-16 (Topic 740) This standard requires entities to recognize the income tax consequences of intra-entity asset transfers when they occur. This removes the exception to postpone recognition until the asset has been sold to an outside party. The updated standard is effective in annual and interim periods in fiscal years beginning after December 15, 2017, with early adoption permitted during the first interim period of a fiscal year. January 1, 2018 The Company intends to apply the modified retrospective approach upon adoption. The Company expects that the adoption of ASU 2016-16 on January 1, 2018 will result in a $15 million cumulative-effect increase in accumulated deficit on its consolidated financial statements and related disclosures. Intangible - Goodwill and Other ASU No. 2017-04 (Topic 350) This standard simplifies the accounting for goodwill and removes Step 2 of the annual goodwill impairment test. Upon adoption, goodwill impairment will be determined based on the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. Early adoption permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017, and requires a prospective transition method. January 1, 2020 The Company does not expect that the adoption of this standard will have a material impact on its consolidated financial statements and related disclosures. Stock Compensation This standard clarifies when to account for a change to the terms or conditions of a share-based payment award as a modification. Under this standard, modification is required only if the fair value, the vesting conditions, or the classification of an award as equity or liability changes as a result of the change in terms or conditions. The updated standard is effective in annual and interim periods in fiscal years beginning after December 15, 2017, with early adoption permitted. January 1, 2018 The Company does not expect that the adoption of ASU 2017-09 will have a material impact to its consolidated financial statements and related disclosures. The Company will adopt the amendment on a prospective basis.

Summary of business and signi23

Summary of business and significant accounting policies (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Schedule of recent accounting pronouncements	Recent accounting standards Standard Description Date of adoption Effect on the financial statements or other significant matters Standards that were adopted Stock Compensation This standard simplifies certain aspects of the accounting for share-based payment transactions, including income taxes, classification of awards and classification on the statement of cash flows. The new guidance also allows an entity to make a policy election to account for forfeitures as they occur. January 1, 2017 Adoption of the standard resulted in the recognition of previously unrecognized excess tax benefits using the modified retrospective method. The Company recorded an increase to U.S. deferred tax assets of $179 million which was recorded directly against the accumulated deficit. The increased deferred tax asset allowed for an offset against long-term income tax payable of $16 million. A full valuation allowance was provided on the remaining U.S. deferred tax asset of $163 million, which was also recorded against the accumulated deficit. The net impact to equity was a decrease in the accumulated deficit of approximately $16 million. The Company elected to apply the change in presentation to the statements of cash flows prospectively and elected to account for forfeitures as they occur. Standards not yet adopted Revenue from Contracts with Customers ASU No. 2014-09, 2015-14, 2016-08, 2016-10 and 2016-12 (Topic 606) The updated revenue standard establishes principles for recognizing revenue and develops a common revenue standard for all industries. Under the new model, recognition of revenue occurs when a customer obtains control of promised goods or services in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The new standard requires that entities disclose the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. Early adoption is permitted, but not earlier than the first quarter of 2017. The retrospective or cumulative effect transition method is permitted. January 1, 2018 The Company completed an analysis of the impact of the standard on its sales contract portfolio by reviewing its current accounting policies and practices to identify differences that would result from applying the requirements of the new standard to its sales contracts. The Company’s analysis of its contracts under the new standard supports the recognition of its product revenue at the time product is shipped, consistent with its current revenue policy. As a result of the adoption of the new guidance, certain sales incentives will need to be estimated as variable consideration at the time product is shipped and included as a reduction to the transaction price. This will result in a reduction of revenue being recorded earlier than under the existing guidance. Additionally, for customers who purchase products directly from the Company's website, the new standard provides for a policy election whereby the Company will record revenue when the related product is shipped. This will result in recognition of revenue earlier than under existing guidance, under which the Company recognizes revenue upon delivery to the customer. The Company expects the net impact of ASU 2014-09 to be less than $5 million as a reduction to retained earnings. The Company will adopt the standard on a modified retrospective basis. Leases ASU No. 2016-02(Topic 842) This standard requires lessees to put most leases on their balance sheets but recognize the expenses on their income statements in a manner similar to current practice. Lessees would recognize a right-to-use asset and lease liability for all leases with terms of more than 12 months. The new standard should be applied on a modified retrospective basis. January 1, 2019 Although the Company is currently evaluating the impact that the adoption of this standard will have on its consolidated financial statements and related disclosures, the Company currently expects that most of its operating lease commitments will be subject to the new standard and recognized as operating lease liabilities and right-of-use assets upon adoption. Income Taxes ASU No. 2016-16 (Topic 740) This standard requires entities to recognize the income tax consequences of intra-entity asset transfers when they occur. This removes the exception to postpone recognition until the asset has been sold to an outside party. The updated standard is effective in annual and interim periods in fiscal years beginning after December 15, 2017, with early adoption permitted during the first interim period of a fiscal year. January 1, 2018 The Company intends to apply the modified retrospective approach upon adoption. The Company expects that the adoption of ASU 2016-16 on January 1, 2018 will result in a $15 million cumulative-effect increase in accumulated deficit on its consolidated financial statements and related disclosures. Intangible - Goodwill and Other ASU No. 2017-04 (Topic 350) This standard simplifies the accounting for goodwill and removes Step 2 of the annual goodwill impairment test. Upon adoption, goodwill impairment will be determined based on the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. Early adoption permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017, and requires a prospective transition method. January 1, 2020 The Company does not expect that the adoption of this standard will have a material impact on its consolidated financial statements and related disclosures. Stock Compensation This standard clarifies when to account for a change to the terms or conditions of a share-based payment award as a modification. Under this standard, modification is required only if the fair value, the vesting conditions, or the classification of an award as equity or liability changes as a result of the change in terms or conditions. The updated standard is effective in annual and interim periods in fiscal years beginning after December 15, 2017, with early adoption permitted. January 1, 2018 The Company does not expect that the adoption of ASU 2017-09 will have a material impact to its consolidated financial statements and related disclosures. The Company will adopt the amendment on a prospective basis.

Fair value measurements (Tables

Fair value measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Assets measured at fair value on recurring basis	The Company’s assets that are measured at fair value on a recurring basis within the fair value hierarchy are summarized as follows: December 31, 2017 December 31, 2016 (in thousands) Level 1 Level 2 Total Level 1 Level 2 Total Cash equivalents (1) : Money market funds $ 25,251 $ — $ 25,251 $ 18,024 $ — $ 18,024 Commercial paper 14,981 — 14,981 — — — Corporate debt securities — 2,500 2,500 — — — Agency securities 4,999 4,999 — — — Total cash equivalents $ 40,232 $ 7,499 $ 47,731 $ 18,024 $ — $ 18,024 Marketable securities: U.S. treasury securities $ — $ 4,995 $ 4,995 $ — $ 8,283 $ 8,283 Commercial paper 19,888 — 19,888 — — — Corporate debt securities — 20,003 20,003 — 15,226 15,226 Municipal securities — — — — 2,330 2,330 Total marketable securities $ 19,888 $ 24,998 $ 44,886 $ — $ 25,839 $ 25,839 (1) Included in cash and cash equivalents in the accompanying consolidated balance sheets. Cash balances were $154.8 million and $174.1 million as of December 31, 2107 and 2016, respectively.

Condensed consolidated financ25

Condensed consolidated financial statement details (Tables)	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Inventory	Inventory (in thousands) December 31, 2017 December 31, 2016 Components $ 18,995 $ 25,236 Finished goods 131,556 141,956 Total inventory $ 150,551 $ 167,192
Property, Plant and Equipment	Property and equipment, net (in thousands) Useful life (in years) December 31, 2017 December 31, 2016 Leasehold improvements 1–11 $ 67,713 $ 48,103 Production, engineering and other equipment 4 47,502 46,328 Tooling 1–2 24,871 23,742 Computers and software 2 20,636 18,750 Furniture and office equipment 3 14,895 12,530 Tradeshow equipment and other 2–5 7,237 7,578 Construction in progress 347 1,870 Gross property and equipment 183,201 158,901 Less: Accumulated depreciation and amortization (114,614 ) (82,392 ) Property and equipment, net $ 68,587 $ 76,509
Schedule of Finite-Lived Intangible Assets	Intangible assets Useful life (in months) December 31, 2017 (in thousands) Gross carrying value Accumulated amortization Net carrying value Purchased technology 24–72 $ 49,901 $ (26,017 ) $ 23,884 In-process research and development (IPR&D) 615 — 615 Total intangible assets $ 50,516 $ (26,017 ) $ 24,499 Useful life (in months) December 31, 2016 (in thousands) Gross carrying value Accumulated Net carrying value Purchased technology 24–72 $ 47,001 $ (17,086 ) $ 29,915 IPR&D 3,615 — 3,615 Total intangible assets $ 50,616 $ (17,086 ) $ 33,530
Schedule of Future Amortization	Amortization expense was $9.0 million , $9.1 million and $4.2 million in 2017 , 2016 and 2015 , respectively. At December 31, 2017 , expected amortization expense of intangible assets with definite lives for future periods is as follows: (in thousands) Total Year ending December 31, 2018 $ 9,263 2019 8,753 2020 4,998 2021 870 2022 — $ 23,884
Schedule of Other Assets	Other long-term assets (in thousands) December 31, 2017 December 31, 2016 POP displays $ 16,451 $ 27,592 Long-term deferred tax assets 825 106 Income tax receivable — 33,425 Deposits and other 19,738 17,206 Other long-term assets $ 37,014 $ 78,329
Schedule of Accrued Liabilities	Accrued liabilities (in thousands) December 31, 2017 December 31, 2016 Accrued payables (1) $ 44,582 $ 91,655 Employee related liabilities (1) 24,945 42,577 Accrued sales incentives 89,549 40,070 Warranty liability 9,934 11,456 Customer deposits 8,700 4,381 Income taxes payable 1,247 2,756 Purchase order commitments 6,162 4,730 Inventory received 14,470 3,950 Other 13,441 9,748 Accrued liabilities $ 213,030 $ 211,323
Schedule of Product Warranty Liability	The following table summarizes the warranty liability activity: Year ended December 31, (in thousands) 2017 2016 2015 Beginning balances $ 11,945 $ 10,856 $ 6,405 Charged to cost of revenue 20,139 19,272 25,377 Settlements of warranty claims (21,711 ) (18,183 ) (20,926 ) Ending balances $ 10,373 $ 11,945 $ 10,856

Stockholders' equity (Tables)

Stockholders' equity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]	The Company had the following shares of common stock reserved for issuance upon the exercise of equity instruments as of December 31, 2017: (in thousands) December 31, 2017 Stock options outstanding 9,809 Restricted stock units outstanding 9,483 Common stock available for future grants 23,071 Total common stock shares reserved for issuance 42,363

Employee benefit plans (Tables)

Employee benefit plans (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-based Compensation, Stock Options, Activity	A summary of the Company’s stock option activity is as follows: Options outstanding Shares (in thousands) Weighted- average Weighted-average remaining contractual term (in years) Aggregate intrinsic value Outstanding at December 31, 2016 12,379 $ 12.17 5.97 $ 32,772 Granted 1,848 9.28 Exercised (1,329 ) 1.70 Forfeited/Cancelled (3,089 ) 18.15 Outstanding at December 31, 2017 9,809 $ 11.16 6.00 $ 19,971 Vested and expected to vest at December 31, 2017 9,786 $ 11.15 6.00 $ 19,971 Exercisable at December 31, 2017 8,154 $ 10.99 5.45 $ 19,971
Schedule of Share-based Compensation, Restricted Stock Units Award Activity	A summary of the Company’s RSU activity is as follows: Shares (in thousands) Weighted- average grant date fair value Non-vested shares at December 31, 2016 7,970 $ 18.08 Granted 8,740 9.40 Vested (3,862 ) 14.95 Forfeited (3,365 ) 16.62 Non-vested shares at December 31, 2017 9,483 $ 11.87
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	The fair value of stock options granted was estimated as of the grant date using the following assumptions: Year ended December 31, 2017 2016 2015 Volatility 44%–49% 44%–45% 43%–54% Expected term (years) 5.3–5.8 5.2–6.1 5.5–7.0 Risk-free interest rate 1.8%–2.1% 1.2%–2.0% 1.6%–2.0% Dividend yield —% —% —%
Schedule of Share-based Payment Award, Equity Instruments Other Than Options, Valuation Assumptions [Table Text Block]	The fair value of stock purchase rights granted under the ESPP was estimated using the following assumptions: Year ended December 31, 2017 2016 2015 Volatility 33%–36% 43%–54% 39%–45% Expected term (years) 0.5 0.5 0.5 Risk-free interest rate 0.7%–1.2% 0.4%–0.5% 0.1%–0.2% Dividend yield —% —% —%
Allocation of Stock-based Compensation Expense	The following table summarizes stock-based compensation included in the consolidated statements of operations: Year ended December 31, (in thousands) 2017 2016 2015 Cost of revenue $ 1,935 $ 1,616 $ 1,492 Research and development 24,963 31,365 18,024 Sales and marketing 10,498 13,883 13,762 General and administrative 13,859 22,663 47,402 Total stock-based compensation expense $ 51,255 $ 69,527 $ 80,680

Net loss per share (Tables)

Net loss per share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Schedule of Net Income per Share, Basic and Diluted	The following table presents the calculations of basic and diluted net income (loss) per share: Year ended December 31, (in thousands, except per share data) 2017 2016 2015 Numerator: Net income (loss) $ (182,873 ) $ (419,003 ) $ 36,131 Denominator: Weighted-average common shares—basic for Class A and Class B common stock 138,056 139,425 134,595 Effect of dilutive stock-based awards — — 11,891 Weighted-average common shares—diluted for Class A and Class B common stock 138,056 139,425 146,486 Net income (loss) per share Basic $ (1.32 ) $ (3.01 ) $ 0.27 Diluted $ (1.32 ) $ (3.01 ) $ 0.25
Schedule of Antidilutive Securities Excluded from Computation of Net Income per Share	The following potentially dilutive shares were not included in the calculation of diluted shares outstanding as the effect would have been anti-dilutive: Year ended December 31, (in thousands) 2017 2016 2015 Effect of anti-dilutive stock-based awards 18,994 21,000 2,681

Income taxes (Tables)

Income taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Income before Income Tax, Domestic and Foreign	Income (loss) before income taxes consisted of the following: Year ended December 31, (in thousands) 2017 2016 2015 Domestic $ (123,325 ) $ (200,595 ) $ 13,562 Foreign (53,062 ) (174,579 ) 39,023 $ (176,387 ) $ (375,174 ) $ 52,585
Schedule of Components of Income Tax Expense (Benefit)	Income tax expense consisted of the following: Year ended December 31, (in thousands) 2017 2016 2015 Current Federal $ (1,857 ) $ (2,925 ) $ 18,548 State 240 (356 ) 3,007 Foreign 10,631 8,542 6,539 Total current 9,014 5,261 28,094 Deferred Federal (248 ) 37,573 (11,211 ) State — 4,436 (204 ) Foreign (2,280 ) (3,441 ) (225 ) Total deferred (2,528 ) 38,568 (11,640 ) Income tax expense $ 6,486 $ 43,829 $ 16,454
Schedule of Effective Income Tax Rate Reconciliation	Year ended December 31, 2017 2016 2015 (dollars in thousands) $ % $ % $ % Reconciliation to statutory rate Tax at federal statutory rate $ (61,735 ) (35.0 )% $ (131,311 ) (35.0 )% $ 18,405 35.0 % Change in valuation allowance (38,016 ) (21.6 ) 101,878 27.2 8,555 16.3 DTA rate change impact due to TCJA 74,943 42.5 — — — — Impact of foreign operations 34,039 19.3 84,491 22.5 6,434 12.2 Stock-based compensation 12,001 6.8 15,718 4.2 2,390 4.5 State taxes, net of federal benefit (6,469 ) (3.7 ) (14,195 ) (3.8 ) 1,454 2.8 Tax credits (9,957 ) (5.6 ) (12,992 ) (3.5 ) (21,891 ) (41.6 ) Other 1,680 1.0 240 0.1 1,107 2.1 Income tax provision at effective tax rate $ 6,486 3.7 % $ 43,829 11.7 % $ 16,454 31.3 %
Schedule of Deferred Tax Assets and Liabilities	Significant components of the Company’s deferred tax assets and liabilities were as follows: Year ended December 31, (in thousands) 2017 2016 Deferred tax assets: Net operating loss carryforwards $ 113,378 $ 30,193 Tax credit carryforwards 66,983 22,341 Stock-based compensation 13,055 26,656 Allowance for returns 5,452 6,336 Intangible assets 770 — Accruals and reserves 18,981 26,587 Total deferred tax assets 218,619 112,113 Valuation allowance (217,884 ) (110,433 ) Total deferred tax assets, net of valuation allowance 735 1,680 Deferred tax liabilities: Depreciation and amortization (292 ) (1,714 ) Intangible assets — (2,540 ) Total deferred tax liabilities (292 ) (4,254 ) Net deferred tax assets (liabilities) $ 443 $ (2,574 )
Summary of Income Tax Contingencies	A reconciliation of the beginning and ending amount of the unrecognized income tax benefits are as follows: Year ended December 31, (in thousands) 2017 2016 2015 Gross balance at January 1 $ 56,909 $ 36,273 $ 16,558 Gross increase related to current year tax positions 20,002 20,594 19,948 Gross decrease related to tax rate change for current year tax positions (2,299 ) — — Gross increase related to prior year tax positions — 130 108 Gross decrease related to prior year tax positions (3,927 ) (88 ) (341 ) Gross decrease related to tax rate change for prior year tax positions (12,101 ) — — $ 58,584 $ 56,909 $ 36,273

Commitments, contingencies an30

Commitments, contingencies and guarantees (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Other Commitments	(in thousands) Total 2018 2019 2020 2021 2022 Thereafter Operating leases (1) $ 128,228 $ 22,177 $ 15,056 $ 18,244 $ 17,817 $ 16,693 $ 38,241 Sponsorship commitments (2) 7,256 4,487 2,769 — — — — Other contractual commitments (3) 2,766 2,044 722 — — — — Long-term debt (4) 175,000 — — — — 175,000 — Total contractual cash obligations $ 313,250 $ 28,708 $ 18,547 $ 18,244 $ 17,817 $ 191,693 $ 38,241 (1) The Company leases its facilities under long-term operating leases, which expire at various dates through 2027. (2) The Company enters into multi-year sponsorship agreements with event organizers, resorts and athletes as part of its marketing efforts. (3) The Company enters into other contractual commitments, including software licenses related to the Company’s financial and IT systems which require payments over several years.

Concentrations of risk and ge31

Concentrations of risk and geographic information (Tables)	12 Months Ended
	Dec. 31, 2017
Concentration Risk [Line Items]
Schedule of Accounts, Notes, Loans and Financing Receivable	The following table summarizes the Company’s accounts receivables sold, without recourse, and factoring fees paid: Year ended December 31, (in thousands) 2017 2016 2015 Accounts receivable sold $ 178,300 $ 167,769 $ 194,223 Factoring fees 1,630 1,266 1,566
Schedule of Revenue by Geographic Region	Revenue by geographic region, based on ship-to destinations, was as follows: Year ended December 31, (in thousands) 2017 2016 2015 Americas $ 591,879 $ 619,784 $ 868,772 Europe, Middle East and Africa (EMEA) 334,872 366,352 535,260 Asia and Pacific (APAC) 252,990 199,345 215,939 Total revenue $ 1,179,741 $ 1,185,481 $ 1,619,971
Accounts Receivable [Member]
Concentration Risk [Line Items]
Schedules of Customer Concentration by Risk Factor	Customers who represented 10% or more of the Company’s net accounts receivable balance were as follows: December 31, 2017 December 31, 2016 Customer A 16% 15% Customer B 32% 27% Customer C 12% * Customer D 11% *
Sales Revenue [Member]
Concentration Risk [Line Items]
Schedules of Customer Concentration by Risk Factor	Customers who represented 10% or more of the Company’s total revenue were as follows: Year ended December 31, 2017 2016 2015 Customer A 15% 17% 14% Customer B * 11% 12% * Less than 10% of total revenue for the period indicated

Restructuring charges (Tables)

Restructuring charges (Tables)	12 Months Ended
	Dec. 31, 2017
Restructuring and Related Activities [Abstract]
Restructuring and Related Costs	Restructuring charges for each period were as follows: Twelve months ended (in thousands) December 31, 2017 December 31, 2016 Cost of revenue $ 634 $ 497 Research and development 10,092 17,197 Sales and marketing 7,047 12,064 General and administrative 2,519 13,331 Total restructuring charges $ 20,292 $ 43,089
Schedule of Restructuring Reserve by Type of Cost	The following table provides a summary of the Company’s restructuring activities during 2017 and the related liabilities recorded in accrued liabilities on the consolidated balance sheet. (in thousands) Severance Other Total Restructuring liability as of December 31, 2016 $ 9,660 $ 879 $ 10,539 Restructuring charges 2,134 1,055 3,189 Cash paid (11,411 ) (1,884 ) (13,295 ) Non-cash reductions 17 — 17 Restructuring liability as of December 31, 2017 $ 400 $ 50 $ 450 The following table provides a summary of the Company’s restructuring activities during 2017 and the related liabilities recorded in accrued liabilities on the consolidated balance sheet. (in thousands) Severance Other Total Restructuring liability as of December 31, 2016 $ — $ — $ — Restructuring charges 10,312 6,654 16,966 Cash paid (9,509 ) (151 ) (9,660 ) Non-cash reductions (803 ) (2,953 ) (3,756 ) Restructuring liability as of December 31, 2017 $ — $ 3,550 $ 3,550

Summary of business and signi33

Summary of business and significant accounting policies (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Allowance for Doubtful Accounts Receivable, Current		$ 0.8	$ 1.3
Amortization of Long-term Assets		$ 19.2	19.6	$ 16.8
Warranty Period		12 months
Advertising Expense		$ 61.3	106	$ 64.7
Effective tax rate reconciliation, share based compensation, excess tax benefit			179
Minimum [Member]
Property, Plant and Equipment [Line Items]
Long-term Assets, Amortization Period		24 months
Useful Life		1 year
Maximum [Member]
Property, Plant and Equipment [Line Items]
Long-term Assets, Amortization Period		36 months
Useful Life		11 years
Accounting Standards Update 2014-09, 2016-08, 2016-10, 2016-12 [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Sales incentives	$ 5
New Accounting Pronouncement, Early Adoption, Effect [Member] | Accounting Standards Update 2016-09 [Member]
Property, Plant and Equipment [Line Items]
Deferred tax liability			16
Deferred income tax assets			163
New Accounting Pronouncement, Early Adoption, Effect [Member] | Retained Earnings [Member] | Accounting Standards Update 2016-09 [Member]
Property, Plant and Equipment [Line Items]
Cumulative effect of new accounting principle in period of adoption			$ 16
European Union [Member]
Property, Plant and Equipment [Line Items]
Warranty Period		2 years

(Details)

(Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)business_acquisition	Dec. 31, 2015USD ($)
Business Acquisition [Line Items]
Cash consideration	$ 0	$ 104,353	$ 65,405
Goodwill	146,459	146,459
Allocated share-based compensation expense	$ 54,037	$ 69,499	80,583
Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Number of Businesses Acquired | business_acquisition		2
Cash consideration		$ 104,000	70,200
Identifiable intangible assets		17,400	32,300
Net deferred tax liabilities		3,400	4,700
Goodwill		89,000	$ 43,000
Deferred cash and stock compensation		$ 35,000
Award requisite service period		4 years
Allocated share-based compensation expense		$ 22,000

Fair value measurements (Detail

Fair value measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash	$ 154,800	$ 174,100
Marketable securities	44,886	25,839
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of convertible senior notes	172,200
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	47,731	18,024
Marketable securities	44,886	25,839
Fair Value, Measurements, Recurring [Member] | US Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	4,995	8,283
Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	19,888	0
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	20,003	15,226
Fair Value, Measurements, Recurring [Member] | Municipal Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	2,330
Fair Value, Measurements, Recurring [Member] | Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	4,999
Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	14,981
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	25,251	18,024
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	2,500
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	40,232	18,024
Marketable securities	19,888	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | US Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	19,888	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Municipal Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	14,981
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	25,251	18,024
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	7,499	0
Marketable securities	24,998	25,839
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | US Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	4,995	8,283
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	20,003	15,226
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Municipal Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	2,330
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	4,999
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	0	$ 0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	$ 2,500

Condensed consolidated financ36

Condensed consolidated financial statement details - Cash, Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash and Cash Equivalents [Line Items]
Marketable securities	$ 44,886	$ 25,839
Cash	154,800	174,100
Cash and cash equivalents	202,504	192,114	$ 279,672	$ 319,929
Fair Value, Measurements, Recurring [Member]
Cash and Cash Equivalents [Line Items]
Marketable securities	$ 44,886	$ 25,839

Condensed consolidated financ37

Condensed consolidated financial statement details - Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Components	$ 18,995	$ 25,236
Finished goods	131,556	141,956
Total inventory	$ 150,551	$ 167,192

Condensed consolidated financ38

Condensed consolidated financial statement details - Property and Equipment, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Gross property and equipment	$ 183,201	$ 158,901
Less: Accumulated depreciation and amortization	(114,614)	(82,392)
Property and equipment, net	68,587	76,509
Depreciation	32,400	32,400	$ 24,800
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Gross property and equipment	67,713	48,103
Production, engineering and other equipment [Member]
Property, Plant and Equipment [Line Items]
Gross property and equipment	47,502	46,328
Tooling [Member]
Property, Plant and Equipment [Line Items]
Gross property and equipment	24,871	23,742
Computers and software [Member]
Property, Plant and Equipment [Line Items]
Gross property and equipment	20,636	18,750
Furniture and office equipment [Member]
Property, Plant and Equipment [Line Items]
Gross property and equipment	14,895	12,530
Tradeshow Equipment and other [Member]
Property, Plant and Equipment [Line Items]
Gross property and equipment	7,237	7,578
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Gross property and equipment	$ 347	$ 1,870

Condensed consolidated financ39

Condensed consolidated financial statement details - Intangible Assets and Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Impairment of Intangible Assets, Finite-lived		$ 6,300
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying value				$ 49,901	$ 47,001
Accumulated amortization				(26,017)	(17,086)
Net carrying value				23,884	29,915
Indefinite lived intangible assets	$ 3,615	3,615		615	3,615
Intangible Assets, Gross (Excluding Goodwill)				50,516	50,616
Intangible assets, net				24,499	33,530
Indefinite-lived Intangible Assets [Roll Forward]
Balance at December 31, 2016	3,615
Balance at June 30, 2017	615	3,615
Amortization of intangible assets	$ 9,000	$ 9,100	$ 4,200
Goodwill				$ 146,459	$ 146,459

Condensed consolidated financ40

Condensed consolidated financial statement details - Future Amortization (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
2,018	$ 9,263
2,019	8,753
2,020	4,998
2,021	870
2,022	0
Net carrying value	$ 23,884	$ 29,915

Condensed consolidated financ41

Condensed consolidated financial statement details - Goodwill (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Business Combination, Goodwill [Abstract]
Goodwill	$ 146,459	$ 146,459

Condensed consolidated financ42

Condensed consolidated financial statement details - Other Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
POP Displays	$ 16,451	$ 27,592
Long-term deferred tax assets	825	106
Income tax receivable	0	33,425
Deposits and other	19,738	17,206
Other long-term assets	$ 37,014	$ 78,329

Condensed consolidated financ43

Condensed consolidated financial statement details - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued payables	$ 44,582	$ 91,655
Employee related liabilities	24,945	42,577
Accrued sales incentives	89,549	40,070
Warranty liability	9,934	11,456
Customer deposits	8,700	4,381
Income taxes payable	1,247	2,756
Purchase order commitments	6,162	4,730
Inventory received	14,470	3,950
Other	13,441	9,748
Accrued liabilities	$ 213,030	$ 211,323

Condensed consolidated financ44

Condensed consolidated financial statement details - Product Warranty (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Beginning balances	$ 11,945	$ 10,856	$ 6,405
Charged to cost of revenue	20,139	19,272	25,377
Settlements of warranty claims	(21,711)	(18,183)	(20,926)
Ending balances	10,373	11,945	$ 10,856
Product Warranty Accrual, Current	9,934	$ 11,456
Product Warranty Accrual, Noncurrent	$ 400

Financing Arrangements (Details

Financing Arrangements (Details) $ / shares in Units, shares in Millions	Apr. 12, 2017USD ($)$ / sharesshares	Mar. 31, 2016USD ($)	Dec. 31, 2017USD ($)shares	Dec. 31, 2016USD ($)	Jun. 30, 2017
Line of Credit Facility [Line Items]
Proceeds from issuance of Convertible senior notes			$ 175,000,000	$ 0
Convertible debt, equity portion			128,300,000
Convertible debt, long-term debt portion			46,700,000
Long-term debt			$ 130,048,000	0
Payments for Repurchase of Equity, Prepaid Forward	$ 78,000,000
Treasury Shares Acquired, Estimated, Prepaid Forward | shares	9.2		6.6
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Credit agreement, current borrowing capacity		$ 250,000,000
Credit agreement, maximum borrowing capacity		300,000,000
Minimum Fixed Charge Coverage Ratio, minimum balance		$ 25,000,000
Minimum Fixed Charge Coverage Ratio, minimum percent		10.00%
Line of Credit Facility, Remaining Borrowing Capacity			$ 118,000,000	$ 150,000,000
Amount outstanding			0
Convertible Debt [Member]
Line of Credit Facility [Line Items]
Debt instrument	$ 175,000,000		175,000,000
Debt Instrument, Unamortized Discount			$ 41,400,000
Interest rate	3.50%
Debt Instrument, Convertible, Conversion Ratio	94.0071
Debt Instrument, Convertible, Conversion Price | $ / shares	$ 10.64
Effective rate			10.50%
Debt Issuance Costs, Net			$ 5,700,000
Percentage of conversion price of notes					130.00%
Percentage of trading price of notes					98.00%
Long-term debt			130,000,000
Interest Expense, Debt			4,400,000
Amortization of Debt Issuance Costs			600,000
Amortization of Debt Discount (Premium)			5,300,000
Long-term Debt [Member] | Convertible Debt [Member]
Line of Credit Facility [Line Items]
Debt Issuance Costs, Gross			4,200,000
Debt Issuance Costs, Net			3,600,000
Additional Paid-in Capital [Member] | Convertible Debt [Member]
Line of Credit Facility [Line Items]
Debt Issuance Costs, Gross			$ 1,500,000
Minimum [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Unused Capacity, Commitment Fee Percentage		0.25%
Maximum [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Unused Capacity, Commitment Fee Percentage		0.375%
London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Basis Spread on Variable Rate		1.50%
London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Basis Spread on Variable Rate		2.00%
Base Rate [Member] | Minimum [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Basis Spread on Variable Rate		0.50%
Base Rate [Member] | Maximum [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Basis Spread on Variable Rate		1.00%

Stockholders' equity (Details)

Stockholders' equity (Details)	1 Months Ended		4 Months Ended	6 Months Ended	12 Months Ended
	Sep. 30, 2015USD ($)$ / sharesshares	May 31, 2015shares	Apr. 30, 2015shares	Jun. 30, 2015shares	Dec. 31, 2017voteshares	Dec. 31, 2015USD ($)shares	Dec. 31, 2016shares	Sep. 30, 2016shares
Class of Stock [Line Items]
Stock options outstanding (shares)					9,809,000		12,379,000
Common stock available for future grants (shares)					42,363,000
Authorized Amount | $	$ 300,000,000
Treasury Stock, Shares, Acquired	1,500,000
Treasury Stock Acquired, Cost Per Share | $ / shares	$ 23.05
Treasury Stock, Value, Acquired | $	$ 35,600,000					$ 35,613,000
Common Class A [Member]
Class of Stock [Line Items]
Common stock authorized (shares)					500,000,000	500,000,000		500,000,000
Common stock outstanding (shares)					101,000,000	104,647,000		101,034,000
Common Stock, Voting Rights, Number | vote					1
Common Stock, Conversion Ratio					1
Common Class B [Member]
Class of Stock [Line Items]
Common stock authorized (shares)					150,000,000	150,000,000		150,000,000
Common stock outstanding (shares)					36,000,000	36,712,000		35,966,000
Common Stock, Voting Rights, Number | vote					10
Conversion ratio once outstanding shares Less than 10% of Aggregate Shares Outstanding, Conversion Ratio					1
Restricted Stock Units (RSUs) [Member]
Class of Stock [Line Items]
Restricted stock units outstanding (shares)					9,483,000		7,970,000
Restricted Stock and Early-exercised Options [Member]
Class of Stock [Line Items]
Common stock available for future grants (shares)					23,071,000
Chief Executive Officer (CEO) [Member] | Common Class B [Member]
Class of Stock [Line Items]
Shares Contributed to Company Without Consideration		4,700,000	500,000	5,200,000

Employee benefit plans - Narrat

Employee benefit plans - Narrative (Details) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2014shares	Dec. 31, 2017USD ($)plan$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value		$ 57,700	$ 49,500	$ 34,400
Number of Stock-based Employee Compensation Plans | plan		3
Defined Contribution Plan Minimum Annual Contributions Per Employee Percent		1.00%
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent		100.00%
Employer Matching Contribution, Percent of Match		100.00%
Employer Matching Contribution, Percent of Employees' Gross Pay		4.00%
Contributions by Employer		$ 5,500	$ 7,200	$ 5,500
Options granted in period, Weighted Average Grant Date Fair Value | $ / shares		$ 4.06	$ 4.84	$ 18.40
Fair value of options vested		$ 19,500	$ 27,200	$ 26,900
Shares granted (shares) | shares		8,740,000
Allocated share-based compensation expense		$ 54,037	$ 69,499	$ 80,583
ESPP stock issued during period (shares) | shares		934,359	668,107	436,924
ESPP weighted average purchase price of shares purchased (usd per share) | $ / shares		$ 8.02	$ 9.15	$ 26.88
Weighted average price of shares granted (usd per share) | $ / shares		$ 9.40
Unearned stock-based compensation, expected recognition period		2 years
RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average price of shares granted (usd per share) | $ / shares		$ 9.40	$ 12.10	$ 44
RSUs [Member] | Chief Executive Officer (CEO) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (shares) | shares	4,500,000
RSUs [Member] | Vested Immediately [Member] | Chief Executive Officer (CEO) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (shares) | shares	1,500,000
Allocated share-based compensation expense		$ 600	$ 6,400	$ 29,400
RSUs [Member] | Share-based Compensation Award, Tranche Two [Member] | Chief Executive Officer (CEO) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Vesting Period	3 years
Shares granted (shares) | shares	3,000,000
Employee Stock Purchase Plan Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase Price of Common Stock, Percent		85.00%
Stock Options, ESPP and Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unearned stock-based compensation costs		$ 97,300
2014 Equity Incentive Plans [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration Period		10 years
2014 Equity Incentive Plans [Member] | Minimum [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Vesting Period		1 year
2014 Equity Incentive Plans [Member] | Minimum [Member] | RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Vesting Period		2 years
2014 Equity Incentive Plans [Member] | Maximum [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Vesting Period		4 years
2014 Equity Incentive Plans [Member] | Maximum [Member] | RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Vesting Period		4 years

Employee benefit plans - Stock

Employee benefit plans - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Shares (in thousands)
Outstanding at beginning of period (shares)	12,379
Granted (shares)	1,848
Exercised (shares)	(1,329)
Forfeited/Cancelled (shares)	(3,089)
Outstanding at end of period (shares)	9,809	12,379
Weighted- average exercise price
Outstanding at beginning of period (in dollars per share)	$ 12.17
Granted (usd per share)	9.28
Exercised (usd per share)	1.70
Forfeited/Cancelled (usd per share)	18.15
Outstanding at end of period (in dollars per share)	$ 11.16	$ 12.17
Weighted Average Remaining Contractual Term (in years)	6 years	5 years 11 months 19 days
Aggregate intrinsic value (in thousands)	$ 19,971	$ 32,772
Vested and Expected to Vest (shares)	9,786
Vested and Expected to Vest - Weighted Average Exercise Price (in dollars per share)	$ 11.15
Vested and Expected to Vest- Weighted Average Remaining Contractual Term	6 years
Vested and Expected to Vest - Aggregate Intrinsic Value	$ 19,971
Exercisable (shares)	8,154
Exercisable - Weighted average exercise price (in dollars per share)	$ 10.99
Exercisable - Weighted Average Remaining Contractual Term	5 years 5 months 12 days
Exercisable - Aggregate intrinsic value	$ 19,971

Employee benefit plans - Restri

Employee benefit plans - Restricted Stock Units Activity (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Shares (in thousands)
Granted (shares)	8,740
Vested (shares)	(3,862)
Forfeited (shares)	(3,365)
Weighted- average grant date fair value
Weighted average price of shares granted (usd per share)	$ 9.40
Weighted average price of shares vested (usd per share)	14.95
Weighted average price of shares forfeited (usd per share)	$ 16.62
RSUs [Member]
Shares (in thousands)
Non-vested shares at beginning of period (shares)	7,970
Non-vested shares at end of period (shares)	9,483	7,970
Weighted- average grant date fair value
Non-vested shares at beginning of period (in dollars per share)	$ 18.08
Weighted average price of shares granted (usd per share)	9.40	$ 12.10	$ 44
Non-vested shares at end of period (in dollars per share)	$ 11.87	$ 18.08

Employee benefit plans - Fair V

Employee benefit plans - Fair Value Assumptions for Stock Options (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%	0.00%	0.00%

Employee benefit plans - Fair51

Employee benefit plans - Fair Value Assumptions for Restricted Stock Units and ESPP (Details) - Employee Stock Purchase Plan Shares [Member]	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	6 months	6 months	6 months
Dividend yield	0.00%	0.00%	0.00%

Employee benefit plans - Alloca

Employee benefit plans - Allocation of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 51,255	$ 69,527	$ 80,680
Total tax benefit recognized	0		28,000
Cost of Revenue [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	1,935	1,616	1,492
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	24,963	31,365	18,024
Selling and Marketing [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	10,498	13,883	13,762
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 13,859	$ 22,663	$ 47,402

Net loss per share Additional I

Net loss per share Additional Information (Details) $ in Millions	Apr. 12, 2017USD ($)shares	Dec. 31, 2017USD ($)voteshares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Treasury Shares Acquired, Estimated, Prepaid Forward	9,200,000	6,600,000
Class A [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common Stock, Voting Rights, Number | vote		1
Conversion of Stock, Shares Issued		1
Class B [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common Stock, Voting Rights, Number | vote		10
Convertible Debt [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Debt instrument | $	$ 175	$ 175
Interest rate	3.50%
Maximum number of shares issuable upon conversion of the notes	20,600,000

Net loss per share - Basic and

Net loss per share - Basic and Diluted Net Income per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net income (loss)	$ (182,873)	$ (419,003)	$ 36,131
Denominator:
Weighted-average common shares—basic for Class A and Class B common stock (shares)	138,056	139,425	134,595
Effect of potentially dilutive shares (shares)	0	0	11,891
Weighted-average common shares—diluted for Class A and Class B common stock (shares)	138,056	139,425	146,486
Net income per share attributable to common stockholders - Basic (in dollars per share)	$ (1.32)	$ (3.01)	$ 0.27
Net income per share attributable to common stockholders - Diluted (in dollars per share)	$ (1.32)	$ (3.01)	$ 0.25

Net loss per share - Antidiluti

Net loss per share - Antidilutive Securities Excluded from Computation of Net Income per Share (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Antidilutive securities excluded from computation of earnings per share (shares)	18,994	21,000	2,681

Income taxes - Income before In

Income taxes - Income before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Domestic	$ (123,325)	$ (200,595)	$ 13,562
Foreign	(53,062)	(174,579)	39,023
Income (loss) before income taxes	$ (176,387)	$ (375,174)	$ 52,585

Income taxes - Income Tax Expen

Income taxes - Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ (1,857)	$ (2,925)	$ 18,548
State	240	(356)	3,007
Foreign	10,631	8,542	6,539
Total current	9,014	5,261	28,094
Deferred:
Federal	(248)	37,573	(11,211)
State	0	4,436	(204)
Foreign	(2,280)	(3,441)	(225)
Total deferred	(2,528)	38,568	(11,640)
Income tax expense (benefit)	$ 6,486	$ 43,829	$ 16,454

Income taxes - Reconciliation t

Income taxes - Reconciliation to Federal Statutory Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amount [Abstract]
Tax at federal statutory rate	$ (61,735)	$ (131,311)	$ 18,405
Change in valuation allowance	(38,016)	101,878	8,555
DTA rate change impact	74,943
Impact of foreign operations	34,039	84,491	6,434
Stock-based compensation	12,001	15,718	2,390
State taxes, net of federal benefits	(6,469)	(14,195)	1,454
Tax credits	(9,957)	(12,992)	(21,891)
Other	1,680	240	1,107
Income tax expense (benefit)	$ 6,486	$ 43,829	$ 16,454
Percent [Abstract]
Tax at federal statutory rate	(35.00%)	(35.00%)	35.00%
Change in valuation allowance	(21.60%)	27.20%	16.30%
DTA rate change impact	42.50%
Impact of foreign operations	19.30%	22.50%	12.20%
Stock-based compensation	6.80%	4.20%	4.50%
State taxes, net of federal benefits	(3.70%)	(3.80%)	2.80%
Tax credits	(5.60%)	(3.50%)	(41.60%)
Other	1.00%	0.10%	2.10%
Income tax provision at effective rate	3.70%	11.70%	31.30%

Income taxes - Deferred Tax Ass

Income taxes - Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Net operating loss carryforwards	$ 113,378	$ 30,193
Tax credit carryforwards	66,983	22,341
Stock-based compensation	13,055	26,656
Allowance for returns	5,452	6,336
Intangible assets	770	0
Accruals and reserves	18,981	26,587
Total deferred tax assets	218,619	112,113
Valuation allowance	(217,884)	(110,433)
Total deferred tax assets, net of valuation allowance	735	1,680
Deferred tax liabilities:
Depreciation and amortization	(292)	(1,714)
Intangible assets	0	(2,540)
Total deferred tax liabilities	(292)	(4,254)
Net deferred tax assets	(443)	2,574
Net deferred tax liability	$ 443	$ (2,574)

Income taxes - Unrecognized Inc

Income taxes - Unrecognized Income Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits
Unrecognized Tax Benefits, beginning balance	$ 56,909	$ 36,273	$ 16,558
Gross increase related to current year tax positions	20,002	20,594	19,948
Gross decrease related to tax rate change for current year tax positions	(2,299)	0	0
Gross increase related to prior year tax positions	0	130	108
Gross decrease related to prior year tax positions	(3,927)	(88)	(341)
Gross decrease related to tax rate change for prior year tax positions	(12,101)	0	0
Unrecognized Tax Benefits, ending balance	$ 58,584	$ 56,909	$ 36,273

Income taxes - Narrative (Detai

Income taxes - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Feb. 28, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Loss Carryforwards [Line Items]
DTA rate change impact		$ 74,943
Tax Cuts and Jobs Act of 2017, release of valuation allowance		200
Change in valuation allowance		107,500
Valuation allowance		217,884	$ 110,433
Valuation allowance, decrease due to debt discount		17,500
Operating loss carryforwards, federal		456,100
Net operating loss carryforwards		456,100
Net operating loss carryforward from acquisitions		8,100
Operating loss carryforwards, subject to expiration		1,700
Unrecognized tax benefits		58,584	56,909	$ 36,273	$ 16,558
Unrecognized tax benefits that would impact effective tax rate		19,800	$ 24,100	$ 31,000
Unrecognized tax benefits, decrease resulting from Tax Cuts and Jobs Act of 2017		14,400
Undistributed earnings of foreign subsidiaries		4,500
CALIFORNIA
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, State and Local		210,300
States Other Than California [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, State and Local		233,700
Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforward		39,600
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforward		34,400
Accounting Standards Update 2016-09 [Member]
Operating Loss Carryforwards [Line Items]
Deferred tax assets, noncurrent		163,000
Deferred tax assets current		36,900
Minimum [Member]
Operating Loss Carryforwards [Line Items]
Decrease in unrecognized tax benefits is reasonably possible		15,000
Unrecognized tax benefits, reasonably possible to decrease that would impact effective tax rate		2,000
Maximum [Member]
Operating Loss Carryforwards [Line Items]
Decrease in unrecognized tax benefits is reasonably possible		20,000
Unrecognized tax benefits, reasonably possible to decrease that would impact effective tax rate		$ 3,000
First quarter 2018 restructuring [Member]
Operating Loss Carryforwards [Line Items]
Proceeds from income tax refunds	$ 32,900

Related party transactions (Det

Related party transactions (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2013
Chief Executive Officer (CEO) [Member] | Related Party Transaction, Chartered Aircraft Expenses [Member]
Related Party Transaction [Line Items]
Expense for services rendered	$ 100,000	$ 500,000	$ 700,000
Accounts payable to related party	0
Immediate Family Member of Member of the Board [Member]
Related Party Transaction [Line Items]
Naming rights agreement, period				3 years
Payments to be made to related party for naming rights				$ 600,000
Aggregate payments to related party for naming rights		600,000
Affiliated Entity [Member] | Related Party Transaction, Contract Manufacturing Agreement [Member]
Related Party Transaction [Line Items]
Accounts payable to related party	0	0
Payments to related party vendor	0		$ 200,000
Director [Member]
Related Party Transaction [Line Items]
Expense for services rendered	0	400,000
Accounts payable to related party	$ 0	$ 300,000

Commitments, contingencies an63

Commitments, contingencies and guarantees - Narrative (Details) - Facilities Lease [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Long-term Purchase Commitment [Line Items]
Future minimum sublease rentals	$ 0
Rent expense	$ 19.1	$ 19.8	$ 12.2

Commitments, contingencies an64

Commitments, contingencies and guarantees - Contractual Commitments (Details) $ in Thousands	Dec. 31, 2017USD ($)
Operating Leases, Future Minimum Payments Due
Total	$ 128,228
2,018	22,177
2,019	15,056
2,020	18,244
2,021	17,817
2,022	16,693
Thereafter	38,241
Other Commitments
Total	2,766
2,018	2,044
2,019	722
2,020	0
2,021	0
2,022	0
Thereafter	0
Debt Instruments
Long-term debt	175,000
Long-term Debt, Maturities, Repayments of Principal in Year Five	175,000
Contractual Obligation, Fiscal Year Maturity
Total	313,250
2,018	28,708
2,019	18,547
2,020	18,244
2,021	17,817
2,022	191,693
Thereafter	38,241
Sponsorship commitment [Member]
Other Commitments
Total	7,256
2,018	4,487
2,019	2,769
2,020	0
2,021	0
2,022	0
Thereafter	$ 0

Concentrations of risk and ge65

Concentrations of risk and geographic information - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue, Major Customer [Line Items]
Revenue	$ 1,179,741	$ 1,185,481	$ 1,619,971
United States [Member]
Revenue, Major Customer [Line Items]
Revenue	528,700	554,900	$ 769,200
Outside the United States [Member]
Revenue, Major Customer [Line Items]
Long-lived assets	$ 79,700	$ 76,600

Concentrations of risk and ge66

Concentrations of risk and geographic information - Schedule of Customer Concentration by Risk Factor (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Concentration Risk [Line Items]
Accounts receivable sold	$ 178,300	$ 167,769	$ 194,223
Factoring fees	$ 1,630	$ 1,266	$ 1,566
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Customer A [Member]
Concentration Risk [Line Items]
Concentration risk	16.00%	15.00%
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Customer B [Member]
Concentration Risk [Line Items]
Concentration risk	32.00%	27.00%
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Customer C [Member]
Concentration Risk [Line Items]
Concentration risk	12.00%
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Customer D [Member]
Concentration Risk [Line Items]
Concentration risk	11.00%
Customer Concentration Risk [Member] | Sales Revenue [Member] | Customer A [Member]
Concentration Risk [Line Items]
Concentration risk	15.00%	17.00%	14.00%
Customer Concentration Risk [Member] | Sales Revenue [Member] | Customer B [Member]
Concentration Risk [Line Items]
Concentration risk		11.00%	12.00%

Concentrations of risk and ge67

Concentrations of risk and geographic information - Schedule of Revenue by Geographic Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenue	$ 1,179,741	$ 1,185,481	$ 1,619,971
United States [Member]
Segment Reporting Information [Line Items]
Revenue	528,700	554,900	769,200
Americas [Member]
Segment Reporting Information [Line Items]
Revenue	591,879	619,784	868,772
Europe, Middle East and Africa [Member]
Segment Reporting Information [Line Items]
Revenue	334,872	366,352	535,260
Asia and Pacific Area Countries [Member]
Segment Reporting Information [Line Items]
Revenue	$ 252,990	$ 199,345	$ 215,939

Restructuring charges - Restruc

Restructuring charges - Restructuring Costs (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 6,500	$ 20,292	$ 43,089
Cost of Revenue [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges			634	497
Research and Development [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges			10,092	17,197
Sales and Marketing [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges			7,047	12,064
General and Administrative [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges			2,519	$ 13,331
Non-cancelable Leases, Accelerated Depreciation and Other Charges [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 6,700
First quarter 2017 restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	17,000
Restructuring charges			$ 16,966
First quarter 2017 restructuring [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 10,312

Restructuring charges (Details)

Restructuring charges (Details) $ in Thousands	Nov. 29, 2016	Jan. 12, 2016	Mar. 31, 2017USD ($)	Mar. 31, 2016USD ($)	Jun. 30, 2017USD ($)	Dec. 31, 2017USD ($)employee	Dec. 31, 2016USD ($)
Restructuring Cost and Reserve [Line Items]
Expected percent of positions eliminated		7.00%
Restructuring charges				$ 6,500		$ 20,292	$ 43,089
Non-cancelable Leases, Accelerated Depreciation and Other Charges [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges			$ 6,700
First quarter 2017 restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Positions eliminated | employee						270
Restructuring charges			17,000
Restructuring charges						$ 16,966
First quarter 2017 restructuring [Member] | Employee Severance and Pay Related Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges			$ 10,312
Fourth quarter 2016 restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Expected percent of positions eliminated	15.00%
Expected cost							$ 40,700
Restructuring charges					$ 3,200
Restructuring charges						3,189
Fourth quarter 2016 restructuring [Member] | Employee Severance and Pay Related Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges						$ 2,134

Restructuring charges - Restr70

Restructuring charges - Restructuring Liability (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2017
Fourth quarter 2016 restructuring [Member]
Restructuring Reserve [Roll Forward]
Restructuring liability as of October 1, 2016	$ 10,539	$ 10,539
Restructuring charges		3,189
Cash paid		(13,295)
Non-cash settlements		17
Restructuring liability as of December 31, 2016		450
Fourth quarter 2016 restructuring [Member] | Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Restructuring charges		2,134
Cash paid		(11,411)
Non-cash settlements		17
Restructuring liability as of December 31, 2016		400
Fourth quarter 2016 restructuring [Member] | Other Restructuring [Member]
Restructuring Reserve [Roll Forward]
Restructuring charges		1,055
Cash paid		(1,884)
Non-cash settlements		0
Restructuring liability as of December 31, 2016		50
First quarter 2017 restructuring [Member]
Restructuring Reserve [Roll Forward]
Restructuring liability as of October 1, 2016	0	0
Restructuring charges		16,966
Cash paid		(9,660)
Non-cash settlements		(3,756)
Restructuring liability as of December 31, 2016		3,550
First quarter 2017 restructuring [Member] | Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Restructuring liability as of October 1, 2016	0	0
Restructuring charges	10,312
Cash paid		(9,509)
Non-cash settlements		(803)
Restructuring liability as of December 31, 2016		0
First quarter 2017 restructuring [Member] | Other Restructuring [Member]
Restructuring Reserve [Roll Forward]
Restructuring liability as of October 1, 2016	$ 0	0
Restructuring charges		6,654
Cash paid		(151)
Non-cash settlements		(2,953)
Restructuring liability as of December 31, 2016		$ 3,550

Valuation and Qualifying Acco71

Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 1,300
Balance at End of Year	800	$ 1,300
Allowance for Doubtful Accounts Receivable [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	1,281	1,400	$ 1,250
Charges to Revenue		0	0
Charges to Expense	(263)	40	682
Deductions/Write-offs	(268)	(159)	(532)
Balance at End of Year	750	1,281	1,400
Allowance for Sales Returns [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	20,038	26,280	25,747
Charges to Revenue	55,274	35,136	48,182
Charges to Expense	(48,554)	(41,378)	(47,649)
Deductions/Write-offs	0	0	0
Balance at End of Year	26,758	20,038	26,280
Valuation Allowance of Deferred Tax Assets [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	110,433	8,555	0
Charges to Revenue	145,467
Charges to Expense	(38,016)	101,878	8,555
Deductions/Write-offs	0	0	0
Balance at End of Year	$ 217,884	$ 110,433	$ 8,555

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ in Thousands	Jan. 02, 2018	Feb. 28, 2018	Mar. 31, 2018	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Subsequent Event [Line Items]
Restructuring charges				$ 6,500	$ 20,292	$ 43,089
Income tax benefit					$ (6,486)	$ (43,829)	$ (16,454)
First quarter 2018 restructuring [Member]
Subsequent Event [Line Items]
Positions eliminated	21.00%
Proceeds from income tax refunds		$ 32,900
Minimum [Member] | First quarter 2018 restructuring [Member]
Subsequent Event [Line Items]
Restructuring charges	$ 23,000
Income tax benefit			$ 2,000
Maximum [Member] | First quarter 2018 restructuring [Member]
Subsequent Event [Line Items]
Restructuring charges	$ 33,000
Income tax benefit			$ 3,000