Cover Page - shares	9 Months Ended
Cover Page - shares	Sep. 28, 2019	Oct. 23, 2019
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 28, 2019
Document Transition Report	false
Entity File Number	001-37444
Entity Registrant Name	FITBIT, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-8920744
Entity Address, Address Line One	199 Fremont Street,
Entity Address, Address Line Two	14th Floor
Entity Address, City or Town	San Francisco,
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94105
City Area Code	415
Local Phone Number	513-1000
Title of 12(b) Security	Class A Common Stock, $0.0001 par value
Trading Symbol	FIT
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Central Index Key	0001447599
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Amendment Flag	false
Common Class A
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		228,860,902
Common Class B
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		31,267,322

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 28, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 287,431	$ 473,956
Marketable securities	214,817	249,493
Accounts receivable, net	345,562	414,209
Inventories	245,096	124,871
Income tax receivable	965	6,957
Prepaid expenses and other current assets	33,376	42,325
Total current assets	1,127,247	1,311,811
Property and equipment, net	88,232	106,286
Operating lease right-of-use assets	71,529
Goodwill	60,979	60,979
Intangible assets, net	17,519	23,620
Deferred tax assets	3,925	4,489
Other assets	7,170	8,362
Total assets	1,376,601	1,515,547
Current liabilities:
Accounts payable	263,181	251,657
Accrued liabilities	365,812	437,234
Operating lease liabilities	23,313
Deferred revenue	28,076	29,400
Income taxes payable	986	1,092
Total current liabilities	681,368	719,383
Long-term deferred revenue	6,174	7,436
Long-term operating lease liabilities	70,202
Other liabilities	29,883	52,790
Total liabilities	787,627	779,609
Commitments and contingencies
Stockholders’ equity:
Class A and Class B common stock	26	25
Additional paid-in capital	1,107,659	1,055,046
Accumulated other comprehensive income (loss)	232	(66)
Accumulated deficit	(518,943)	(319,067)
Total stockholders’ equity	588,974	735,938
Total liabilities and stockholders’ equity	$ 1,376,601	$ 1,515,547

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Income Statement [Abstract]
Revenue	$ 347,200	$ 393,575	$ 932,646	$ 940,784
Cost of revenue	239,248	240,061	627,027	554,132
Gross profit	107,952	153,514	305,619	386,652
Operating expenses:
Research and development	65,693	79,840	213,651	256,223
Sales and marketing	71,296	66,676	222,972	239,573
General and administrative	23,083	24,812	74,640	91,111
Total operating expenses	160,072	171,328	511,263	586,907
Operating loss	(52,120)	(17,814)	(205,644)	(200,255)
Interest income, net	2,388	2,072	8,476	5,599
Other income (expense), net	(492)	(5,141)	1,242	(2,366)
Loss before income taxes	(50,224)	(20,883)	(195,926)	(197,022)
Income tax expense (benefit)	1,669	(18,827)	3,950	4,179
Net loss	$ (51,893)	$ (2,056)	$ (199,876)	$ (201,201)
Net loss per share:
Basic (in dollars per share)	$ (0.20)	$ (0.01)	$ (0.78)	$ (0.83)
Diluted (in dollars per share)	$ (0.20)	$ (0.01)	$ (0.78)	$ (0.83)
Shares used to compute net loss per share:
Basic (in shares)	258,753	245,838	256,046	242,746
Diluted (in shares)	258,753	245,838	256,046	242,746

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (51,893)	$ (2,056)	$ (199,876)	$ (201,201)
Cash flow hedges:
Change in unrealized gain (loss) on cash flow hedges, net of tax benefit of $0, $43, $0 and $709, respectively	(66)	868	(66)	6,780
Less: reclassification for realized net loss included in net loss, net of tax benefit of $0, $(115), $0 and $(244), respectively	0	(2,334)	0	(3,362)
Net change, net of tax	(66)	(1,466)	(66)	3,418
Available-for-sale investments:
Change in unrealized gain (loss) on investments	35	120	364	(88)
Less reclassification for realized net gain included in net loss	0	0	0	12
Net change, net of tax	35	120	364	(76)
Comprehensive loss	$ (51,924)	$ (3,402)	$ (199,578)	$ (197,859)

Condensed Consolidated Statements of Comprehensive Loss (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Statement of Comprehensive Income [Abstract]
Change in unrealized gain (loss) on cash flow hedges, tax	$ 0	$ 43	$ 0	$ 709
Reclassification for realized net gains included in net income, tax	$ 0	$ (115)	$ 0	$ (244)

Condensed Consolidated Statements of Stockholders’ Equity - USD ($) $ in Thousands	Total	Common Stock	Additional paid-in capital	Accumulated other comprehensive income (loss)	Accumulated deficit
Beginning balance (in shares) at Dec. 31, 2017		238,756,522
Beginning balance at Dec. 31, 2017	$ 823,963	$ 24	$ 956,060	$ (9)	$ (132,112)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)		8,854,756
Issuance of common stock	11,646	$ 1	11,645
Stock-based compensation expense	73,783		73,783
Taxes related to net share settlement of restricted stock units	(15,685)		(15,685)
Net loss	(201,201)				(201,201)
Other comprehensive loss	3,342			3,342
Ending balance (in shares) at Sep. 29, 2018		247,611,278
Ending balance at Sep. 29, 2018	694,721	$ 25	1,025,803	3,333	(334,440)
Beginning balance (in shares) at Jun. 30, 2018		245,041,726
Beginning balance at Jun. 30, 2018	678,959	$ 25	1,006,639	4,679	(332,384)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)		2,569,552
Issuance of common stock	908	$ 0	908
Stock-based compensation expense	23,954		23,954
Taxes related to net share settlement of restricted stock units	(5,698)		(5,698)
Net loss	(2,056)				(2,056)
Other comprehensive loss	(1,346)			(1,346)
Ending balance (in shares) at Sep. 29, 2018		247,611,278
Ending balance at Sep. 29, 2018	694,721	$ 25	1,025,803	3,333	(334,440)
Beginning balance (in shares) at Dec. 31, 2018		252,362,841
Beginning balance at Dec. 31, 2018	735,938	$ 25	1,055,046	(66)	(319,067)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)		7,522,885
Issuance of common stock	7,045	$ 1	7,044
Stock-based compensation expense	59,064		59,064
Taxes related to net share settlement of restricted stock units	(13,495)		(13,495)
Net loss	(199,876)				(199,876)
Other comprehensive loss	298			298
Ending balance (in shares) at Sep. 28, 2019		259,885,726
Ending balance at Sep. 28, 2019	588,974	$ 26	1,107,659	232	(518,943)
Beginning balance (in shares) at Jun. 29, 2019		258,139,452
Beginning balance at Jun. 29, 2019	625,544	$ 25	1,092,306	263	(467,050)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)		1,746,274
Issuance of common stock	233		232
Stock-based compensation expense	17,971		17,971
Taxes related to net share settlement of restricted stock units	(2,850)		(2,850)
Net loss	(51,893)
Other comprehensive loss	(31)			(31)
Ending balance (in shares) at Sep. 28, 2019		259,885,726
Ending balance at Sep. 28, 2019	$ 588,974	$ 26	$ 1,107,659	$ 232	$ (518,943)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018
Cash Flows from Operating Activities
Net loss	$ (199,876)	$ (201,201)
Adjustments to reconcile net loss to net cash used in operating activities:
Provision for doubtful accounts	29	37
Provision for inventory obsolescence	5,163	9,019
Depreciation	43,215	35,388
Non-cash lease expense	17,961	0
Write-off of property and equipment	169	7,513
Amortization of intangible assets	6,100	5,866
Stock-based compensation	59,175	73,613
Deferred income taxes	618	(1,690)
Impairment of equity investment	0	6,000
Other	(50)	(693)
Changes in operating assets and liabilities, net of acquisition:
Accounts receivable	68,617	80,227
Inventories	(125,500)	(80,064)
Prepaid expenses and other assets	11,872	123,356
Fitbit Force recall reserve	242	(395)
Accounts payable	11,826	16,357
Accrued liabilities and other liabilities	(61,005)	(67,813)
Lease liabilities	(20,975)	0
Deferred revenue	(2,586)	(9,649)
Income taxes payable	(107)	5,653
Net cash provided by (used in) operating activities	(185,112)	1,524
Cash Flows from Investing Activities
Purchase of property and equipment	(26,277)	(40,174)
Purchases of marketable securities	(287,969)	(284,986)
Sales of marketable securities	2,016	93,020
Maturities of marketable securities	322,132	309,323
Acquisition, net of cash acquired	(2,625)	(13,646)
Net cash provided by investing activities	7,277	63,537
Cash Flows from Financing Activities
Repayment of debt	0	(747)
Payment of financing lease liability	(2,239)	0
Proceeds from issuance of common stock	7,044	11,641
Taxes paid related to net share settlement of restricted stock units	(13,495)	(15,684)
Net cash used in financing activities	(8,690)	(4,790)
Net increase (decrease) in cash and cash equivalents	(186,525)	60,271
Cash and cash equivalents at beginning of period	473,956	341,966
Cash and cash equivalents at end of period	$ 287,431	$ 402,237

Basis of Presentation and Summary of Significant Accounting Policies	9 Months Ended
	Sep. 28, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	Basis of Presentation and Summary of Significant Accounting Policies The accompanying condensed consolidated financial statements of Fitbit, Inc. (the “Company”) are unaudited. The condensed consolidated balance sheet at December 31, 2018 has been derived from the audited financial statements of the Company. The accompanying condensed financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) for interim financial information, and in management’s opinion, includes all adjustments, consisting of only normal recurring adjustments, necessary for the fair statement of the Company’s financial position, its results of operations, and cash flows for the interim periods presented. The results of operations for the nine months ended September 28, 2019 are not necessarily indicative of the results to be expected for the full fiscal year or any other period. The accompanying condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2018, filed with the Securities and Exchange Commission (“SEC”) on March 1, 2019. The Company’s fiscal year ends on December 31 of each year. The Company is on a 4-4-5 week quarterly calendar. There were 91 days in each of the three months ended September 28, 2019 and September 29, 2018, respectively. The condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated. Use of Estimates The preparation of condensed consolidated financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported and disclosed in the condensed consolidated financial statements and accompanying notes. The primary estimates and assumptions made by management are related to revenue recognition, reserves for sales returns and incentives, reserves for warranty, valuation of stock-based awards, fair value of derivative assets and liabilities, allowance for doubtful accounts, inventory valuation, fair value of goodwill and acquired tangible and intangible assets and liabilities assumed during acquisitions, the recoverability of intangible assets and their useful lives, contingencies, income taxes, and impairment of an equity investment. Actual results could differ from those estimates, and such differences may be material to the condensed consolidated financial statements. Significant Accounting Policies There have been no significant changes in the Company’s accounting policies from those disclosed in its Annual Report on Form 10-K, except for the policies in relation to the adoption of Accounting Standards Update (“ASU”) 2016-02, Leases (Topic 842), discussed below in the section titled “Accounting Pronouncements Recently Adopted.” Leases The Company determines if an arrangement is a lease at inception. Operating lease right-of-use assets (“ROU assets”) and short-term and long-term lease liabilities are included on the face of the condensed consolidated balance sheet. Finance lease ROU assets are presented within other assets, and finance lease liabilities are presented within accrued liabilities. ROU assets represent the right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit rate, the Company uses an incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The operating lease ROU asset also excludes lease incentives. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The Company has lease agreements with lease and non-lease components, which are accounted for as a single lease component. For lease agreements with terms less than 12 months, the Company has elected the short-term lease measurement and recognition exemption, and it recognizes such lease payments on a straight-line basis over the lease term. Recent Accounting Pronouncements Accounting Pronouncements Not Yet Adopted In June 2016, the Financial Accounting Standards Board (the “FASB”) issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. ASU 2016-13 provides for a new impairment model which requires measurement and recognition of expected credit losses for most financial assets and certain other instruments, including but not limited to accounts receivable and available for sale debt securities. In May 2019, the FASB issued ASU 2019-05, Financial Instruments-Credit Losses (Topic 326): Targeted Transition Relief. This ASU provides an option to irrevocably elect to measure certain individual financial assets at fair value instead of amortized cost. ASU 2016-13 and ASU 2019-05 will become effective for the Company on January 1, 2020 and early adoption is permitted. The Company is currently evaluating the impact of this guidance on its consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment. ASU 2017-04 simplifies the subsequent measurement of goodwill by eliminating the second step of the goodwill impairment test. The second step measures a goodwill impairment loss by comparing the implied fair value of a reporting unit’s goodwill with the carrying amount of that goodwill. Under ASU 2017-04, a company will record an impairment charge based on the excess of a reporting unit’s carrying amount over its fair value. ASU 2017-04 will be applied prospectively and is effective for annual or interim goodwill impairment tests in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company does not expect adoption of this guidance will have a material impact on its consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement. ASU 2018-13 modifies the disclosure requirements on fair value measurements and will become effective for the Company on January 1, 2020 and early adoption is permitted. The Company is currently evaluating the impact of this guidance on its consolidated financial statements. In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. ASU 2018-15 clarifies the accounting for implementation costs in cloud computing arrangements and will become effective for the Company on January 1, 2020 and early adoption is permitted. The Company is currently evaluating the impact of this guidance on its consolidated financial statements. In April 2019, the FASB issued ASU No. 2019-04, Codification Improvements to Topic 326, Financial Instruments – Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments. This ASU clarifies and corrects guidance related to Topic 326, Topic 815, and Topic 825. The applicable provisions of this ASU will become effective for the Company on January 1, 2020. The Company is currently evaluating the impact of this guidance on its consolidated financial statements. Accounting Pronouncements Recently Adopted In February 2016, the FASB issued ASU 2016-02, Leases and subsequent amendments to the initial guidance; ASU 2017-13, ASU 2018-10 and ASU 2018-11 (collectively, “Topic 842”). Topic 842 requires lessees to recognize ROU assets and lease liabilities for operating leases, initially measured at the present value of the lease payments, on the balance sheet. The Company adopted the standard effective January 1, 2019 using a modified retrospective approach. Prior periods were not retrospectively adjusted. The cumulative effect upon adoption on the opening accumulated deficit balance was zero. The Company elected the available practical expedients, which allowed for carryforward of historical assessments of whether contracts contain or are leases, historical lease classification, and remaining lease terms. The standard had a material impact on the Company’s condensed consolidated balance sheets but did not have an impact on its condensed consolidated statements of operations. The most significant impact was the recognition of ROU assets and short-term and long-term lease liabilities for operating leases. The balances of operating lease ROU assets, operating lease liabilities, and long-term operating lease liabilities as of September 28, 2019 were $71.5 million, $23.3 million, and $70.2 million, respectively. The impact to other financial statement line items was immaterial. Adoption of the standard had no impact to net cash from or used in operating, investing, or financing activities in the Company’s consolidated statement of cash flows. Refer to Note 5 for further information on leases. In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities. ASU 2017-12 amends the hedge accounting rules to simplify the application of hedge accounting standard and better portray the economic results of risk management activities in the financial statements. The standard expands the ability to hedge non-financial and financial risk components, reduces complexity in fair value hedges of interest rate risk, eliminates the requirement to separately measure and report hedge ineffectiveness, as well as eases certain hedge effectiveness assessment requirements. ASU 2017-12 became effective for the Company on January 1, 2019 with early adoption permitted. The Company early adopted this new standard in the first quarter of 2018. The adoption of this standard did not have a material impact on the Company’s consolidated financial statements. In June 2018, the FASB issued ASU 2018-07, Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting. ASU 2018-07 expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. ASU 2018-07 became effective for the Company on January 1, 2019. The adoption of this standard did not have a material impact on the Company’s consolidated financial statements.

Fair Value Measurements

9 Months Ended

Sep. 28, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

The carrying values of the Company’s accounts receivable, accounts payable, and accrued liabilities approximated their fair values due to the short period of time to maturity or repayment.

The following tables set forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands):



	September 28, 2019
	Level 1		Level 2		Level 3		Total

Assets:
Money market funds	$	95,079	$	—	$	—	$	95,079
U.S. government agencies	—		83,246		—		83,246
Corporate debt securities	—		222,823		—		222,823
Derivative assets	—		775		—		775
Total	$	95,079	$	306,844	$	—	$	401,923
Liabilities:
Derivative liabilities	$	—	$	9	$	—	$	9
Total	$	—	$	9	$	—	$	9



	December 31, 2018
	Level 1		Level 2		Level 3		Total

Assets:
Money market funds	$	273,546	$	—	$	—	$	273,546
U.S. government agencies	—		72,840		—		72,840
Corporate debt securities	—		228,953		—		228,953
Derivative assets	—		623		—		623
Total	$	273,546	$	302,416	$	—	$	575,962
Liabilities:
Derivative liabilities	$	—	$	549	$	—	$	549
Stock warrant liability	—		—		410		410
Total	$	—	$	549	$	410	$	959

The fair value of the Company’s Level 1 financial instruments is based on quoted market prices in active markets for identical instruments. The fair value of the Company’s Level 2 financial instruments is based on observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data.

In addition, Level 2 assets and liabilities include derivative financial instruments associated with hedging activity, which are further discussed in Note 3. Derivative financial instruments are initially measured at fair value on the contract date and are subsequently remeasured to fair value at each reporting date using inputs such as spot rates, forward rates, and discount rates. There is not an active market for each hedge contract, but the inputs used to calculate the value of the instruments are tied to active markets.

There were no Level 3 assets as of September 28, 2019 and December 31, 2018. There were no Level 3 liabilities as of September 28, 2019 and there were Level 3 liabilities as of December 31, 2018. There were no transfers between fair value measurement levels during the three and nine months ended September 28, 2019 and September 29, 2018.

- Definition

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

+ References + Details

Financial Instruments

9 Months Ended

Sep. 28, 2019

Investments, Debt and Equity Securities [Abstract]

Financial Instruments

Cash, Cash Equivalents and Marketable Securities

The Company’s marketable securities are classified as available-for-sale as of the balance sheet date and are reported at fair value with unrealized gains and losses reported, net of tax, as a separate component of accumulated other comprehensive income (loss) in stockholders’ equity. Because the Company views marketable securities as available to support current operations as needed, it has classified all available-for-sale securities as current assets. Realized gains or losses and other-than-temporary impairments, if any, on available-for-sale securities are reported in other income (expense), net, as incurred.

Investments are reviewed periodically to identify potential other-than-temporary impairments. No impairment loss has been recorded on the securities included in the tables below because the Company believes that the decrease in fair value of these securities is temporary and expects to recover up to, or beyond, the initial cost of investment for these securities.

The following table sets forth cash, cash equivalents and marketable securities as of September 28, 2019 (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Cash and Cash Equivalents		Marketable Securities

Cash	$	101,100	$	—	$	—		$	101,100	$	101,100	$	—
Money market funds	95,079		—		—			95,079		95,079		—
U.S. government agencies	83,190		61		(5		)	83,246		18,232		65,014
Corporate debt securities	222,712		124		(13		)	222,823		73,020		149,803
Total	$	502,081	$	185	$	(18	)	$	502,248	$	287,431	$	214,817

The following table sets forth cash, cash equivalents and marketable securities as of December 31, 2018 (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Cash and Cash Equivalents		Marketable Securities

Cash	$	148,110	$	—	$	—		$	148,110	$	148,110	$	—
Money market funds	273,546		—		—			273,546		273,546		—
U.S. government agencies	72,884		1		(45		)	72,840		9,738		63,102
Corporate debt securities	229,040		—		(87		)	228,953		42,562		186,391
Total	$	723,580	$	1	$	(132	)	$	723,449	$	473,956	$	249,493

The gross unrealized gains or losses on marketable securities as of September 28, 2019 and December 31, 2018 were not material. There were no available-for-sale investments as of September 28, 2019 and December 31, 2018 that have been in a continuous unrealized loss position for greater than 12 months on a material basis.

The following table classifies marketable securities by contractual maturities (in thousands):



	September 28, 2019		December 31, 2018

Due in one year	$	205,923	$	249,493
Due in one to two years	8,894		—
Total	$	214,817	$	249,493

Derivative Financial Instruments

The Company operates in foreign countries, which exposes it to market risk associated with foreign currency exchange rate fluctuations between the U.S. dollar and various foreign currencies. In order to manage this risk, the Company may hedge a portion of its foreign currency exposures related to outstanding monetary assets and liabilities as well as forecasted revenues and expenses, using foreign currency exchange forward or option contracts. In general, the market risk related to these contracts is offset by corresponding gains and losses on the hedged transactions. The Company does not enter into derivative contracts for trading or speculative purposes.

Cash Flow Hedges

The Company at times enters into foreign currency derivative contracts designated as cash flow hedges to hedge certain forecasted revenue and expense transactions denominated in currencies other than the U.S. dollar. The Company’s cash flow hedges consist of forward contracts with maturities of 12 months or less.

The Company periodically assesses the effectiveness of its cash flow hedges. Effectiveness represents a derivative instrument’s ability to generate offsetting changes in cash flows related to the hedged risk. The Company records the gains or losses, net of tax, related to its cash flow hedges as a component of accumulated other comprehensive income (loss) in stockholders’ equity and subsequently reclassifies the gains or losses into revenue when the underlying hedged transactions are recognized. If the hedged transaction becomes probable of not occurring, the corresponding amounts in accumulated other comprehensive income (loss) would immediately be reclassified to other income (expense), net. Cash flows related to the Company’s cash flow hedging program are recognized as cash flows from operating activities in its statements of cash flows.

The Company had no outstanding contracts that were designated as cash flow hedges for forecasted revenue as of September 28, 2019 and December 31, 2018, respectively.

Balance Sheet Hedges

The Company enters into foreign exchange contracts to hedge certain monetary assets and liabilities that are denominated in currencies other than the functional currency of its subsidiaries. These foreign exchange contracts are carried at fair value, do not qualify for hedge accounting treatment, and are not designated as hedging instruments. Changes in the value of the foreign exchange contracts are recognized in other income (expense), net, and offset the foreign currency gain or loss on the underlying net monetary assets or liabilities.

The Company had outstanding balance sheet hedges with a total notional amount of $118.6 million and $101.4 million as of September 28, 2019 and December 31, 2018, respectively.

Fair Value of Foreign Currency Derivatives

The foreign currency derivative contracts that were not settled at the end of the period are recorded at fair value, on a gross basis, in the condensed consolidated balance sheets. The following table presents the fair value of the Company’s foreign currency derivative contracts as of the periods presented (in thousands):



		September 28, 2019				December 31, 2018
	Balance Sheet Location	Fair Value Derivative Assets		Fair Value Derivative Liabilities		Fair Value Derivative Assets		Fair Value Derivative Liabilities

Hedges not designated	Prepaid expenses and other current assets	$	775	$	—	$	623	$	—
Hedges not designated	Accrued liabilities	—		9		—		549
Total fair value of derivative instruments		$	775	$	9	$	623	$	549

Financial Statement Effect of Foreign Currency Derivative Contracts

The following table presents the pre-tax impact of the Company’s foreign currency derivative contracts on other comprehensive income (“OCI”) and the condensed consolidated statements of operations for the periods presented (in thousands):



		Three Months Ended				Nine Months Ended
	Income Statement Location	September 28, 2019		September 29, 2018		September 28, 2019		September 29, 2018

Foreign exchange cash flow hedges:
Gain recognized in OCI – effective portion		$	—	$	911	$	—	$	7,489
Gain reclassified from OCI into income – effective portion	Revenue	—		2,449		—		3,606

Foreign exchange balance sheet hedges:
Gain recognized in income	Other income, net	$	2,041	$	1,035	$	1,567	$	3,335

As of September 28, 2019, there were no net derivative gains related to the Company’s cash flow hedges to be reclassified from OCI into revenue within the next 12 months.

Effect of Derivative Contracts on Condensed Consolidated Statements of Operations

The following table provides the location in the condensed consolidated statements of operations and amount of the recognized gains or losses to the Company’s derivative instruments designated as hedging instruments (in thousands):



	Three Months Ended				Nine Months Ended
	September 28, 2019		September 29, 2018		September 28, 2019		September 29, 2018

Total amounts presented in the condensed consolidated statement of operations in which the effects of cash flow hedges are recorded in revenue	$	347,200	$	393,575	$	932,646	$	940,784
Total amounts presented in the condensed consolidated statement of operations in which the effects of cash flow hedges are recorded in operating expenses	160,072		171,328		511,263		586,907
Gains on foreign exchange contracts designated as cash flow hedges reclassified from OCI into revenue	—		2,449		—		3,606

Offsetting of Foreign Currency Derivative Contracts

The Company presents its derivative assets and derivative liabilities at gross fair values in the condensed consolidated balance sheets. The Company generally enters into master netting arrangements, which mitigate credit risk by permitting net settlement of transactions with the same counterparty. The Company is not required to pledge, and is not entitled to receive, cash collateral related to these derivative instruments.

The following tables set forth the available offsetting of net derivative assets under the master netting arrangements as of September 28, 2019 and December 31, 2018 (in thousands):



	September 28, 2019
	Gross Amounts Offset in the Condensed Consolidated Balance Sheets						Gross Amounts Not Offset in Condensed Consolidated Balance Sheets
	Gross Amounts Recognized		Gross Amounts Offset		Net Amounts Presented		Financial Instruments		Cash Collateral Received		Net Amount

Foreign exchange contracts assets	$	775	$	—	$	775	$	9	$	—	$	766
Foreign exchange contracts liabilities	9		—		9		9		—		—

	December 31, 2018
	Gross Amounts Offset in the Condensed Consolidated Balance Sheets						Gross Amounts Not Offset in Condensed Consolidated Balance Sheets
	Gross Amounts Recognized		Gross Amounts Offset		Net Amounts Presented		Financial Instruments		Cash Collateral Received		Net Amount

Foreign exchange contracts assets	$	623	$	—	$	623	$	549	$	—	$	74
Foreign exchange contracts liabilities	549		—		549		549		—		—

Balance Sheet Components

9 Months Ended

Sep. 28, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Balance Sheet Components

Deferred Revenue

Deferred revenue relates to performance obligations for which payments have been received by the customer prior to revenue recognition. Deferred revenue primarily consists of deferred software, or amounts allocated to mobile dashboard and on-line apps and unspecified upgrade rights. Deferred revenue also includes deferred subscription-based services. The deferred software and deferred subscription-based service performance obligations are anticipated to be recognized over the useful life or service periods of twelve to seventeen months.

Changes in the total short-term and long-term deferred revenue balances were as follows (in thousands):



	Three Months Ended			Nine Months Ended
	September 28, 2019			September 28, 2019

Beginning balances	$	33,361		$	36,836
Deferral of revenue	10,515			27,325
Recognition of deferred revenue	(9,626		)	(29,911		)
Ending balances	$	34,250		$	34,250

Revenue Returns Reserve

Revenue returns reserve activities were as follows (in thousands):



	Three Months Ended						Nine Months Ended
	September 28, 2019			September 29, 2018			September 28, 2019			September 29, 2018

Beginning balances	$	75,044		$	74,996		$	104,001		$	109,872
Increases ⁽¹⁾	41,945			43,383			119,070			106,385
Returns taken	(42,845		)	(39,862		)	(148,927		)	(137,740		)
Ending balances	$	74,144		$	78,517		$	74,144		$	78,517


⁽¹⁾	Increases in the revenue returns reserve include provisions for open box returns and stock rotations.

Inventories

Inventories consisted of the following (in thousands):



	September 28, 2019		December 31, 2018

Components	$	6,504	$	8,866
Finished goods	238,592		116,005
Total inventories	$	245,096	$	124,871

Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following (in thousands):



	September 28, 2019		December 31, 2018

Prepaid expenses	$	10,841	$	18,100
Point-of-purchase (“POP”) displays, net	3,467		5,143
Prepaid marketing	2,941		3,258
Derivative asset	775		623
Other	15,352		15,201
Total prepaid expenses and other current assets	$	33,376	$	42,325

Property and Equipment, Net

Property and equipment, net, consisted of the following (in thousands):




	September 28, 2019			December 31, 2018

Tooling and manufacturing equipment	$	98,773		$	80,685
Furniture and office equipment	20,015			22,738
Purchased and internally-developed software	26,634			21,741
Leasehold improvements	59,741			67,715
Total property and equipment	205,163			192,879
Less: Accumulated depreciation and amortization	(116,931		)	(86,593		)
Property and equipment, net	$	88,232		$	106,286

Total depreciation expense related to property and equipment, net was $13.1 million and $11.8 million for the three months ended September 28, 2019 and September 29, 2018, respectively, and $43.2 million and $35.4 million for the nine months ended September 28, 2019 and September 29, 2018, respectively.

Goodwill and Intangible Assets

The carrying amount of goodwill was $61.0 million as of September 28, 2019 and December 31, 2018.

The carrying amounts of the intangible assets as of September 28, 2019 and December 31, 2018 were as follows (in thousands):



	September 28, 2019							December 31, 2018
	Gross		Accumulated Amortization			Net		Gross		Accumulated Amortization			Net

Developed technology	$	35,988	$	(21,506	)	$	14,482	$	35,988	$	(15,983	)	$	20,005
Customer relationships	3,790		(857		)	2,933		3,790		(451		)	3,339
Trademarks and other	1,278		(1,174		)	104		1,278		(1,002		)	276
Total intangible assets, net	$	41,056	$	(23,537	)	$	17,519	$	41,056	$	(17,436	)	$	23,620

Total amortization expense related to intangible assets was $2.0 million and $2.1 million for the three months ended September 28, 2019 and September 29, 2018, respectively, and $6.1 million and $5.9 million for the nine months ended September 28, 2019 and September 29, 2018, respectively.

The estimated future amortization expense of acquired finite-lived intangible assets to be charged to cost of revenue and operating expenses after September 28, 2019 is as follows (in thousands):



	Cost of Revenue		Operating Expenses		Total

Remaining 2019	$	2,392	$	207	$	2,599
2020	6,192		643		6,835
2021	4,504		597		5,101
2022	955		597		1,552
2023	—		597		597
Thereafter	—		835		835
Total finite-lived intangible assets, net	$	14,043	$	3,476	$	17,519

Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):



	September 28, 2019		December 31, 2018
	September 28, 2019		December 31, 2018
Accrued sales incentives	$	92,087	$	126,400
Accrued revenue reserve from returns	74,144		104,001
Product warranty	44,904		45,605
Accrued manufacturing expense and freight	36,952		21,357
Accrued sales and marketing	29,725		18,171
Accrued co-op advertising and marketing development funds	27,783		30,435
Accrued research and development	16,521		8,783
Sales taxes and VAT payable	14,108		20,121
Employee-related liabilities	13,513		33,916
Inventory received but not billed	4,397		6,373
Accrued legal settlements and fees	3,375		2,821
Finance lease liabilities	464		—
Derivative liabilities	9		549
Other	7,830		18,702
Accrued liabilities	$	365,812	$	437,234

Product warranty reserve activities were as follows (in thousands):



	Three Months Ended						Nine Months Ended
	September 28, 2019			September 29, 2018			September 28, 2019			September 29, 2018

Beginning balances	$	45,260		$	50,468		$	45,605		$	87,882
Charged to cost of revenue	11,019			9,245			28,247			(1,722		)
Changes related to pre-existing warranties	2,201			(1,354		)	4,874			(9,226		)
Settlement of claims	(13,576		)	(10,504		)	(33,822		)	(29,079		)
Ending balances	$	44,904		$	47,855		$	44,904		$	47,855

Accumulated Other Comprehensive Income (Loss)

The components and activity of accumulated other comprehensive income (“AOCI”), net of tax, were as follows (in thousands):



	Unrealized Gains (Losses) on Cash Flow Hedges			Currency Translation Adjustments		Unrealized Gains (Losses) on Available-for-Sale Investments			Total

Balance at December 31, 2018	$	66		$	—	$	(132	)	$	(66	)
Other comprehensive income (loss) before reclassifications	(66		)	—		364			298
Other comprehensive income (loss)	(66		)	—		364			298
Balance at September 28, 2019	$	—		$	—	$	232		$	232

Leases

9 Months Ended

Sep. 28, 2019

Leases [Abstract]

Leases

The Company leases its principal facilities located in San Francisco, California. The Company also leases office space in various locations with expiration dates between 2019 and 2024. The lease agreements often include leasehold improvement incentives, escalating lease payments, renewal provisions and other provisions which require the Company to pay taxes, insurance, maintenance costs or defined rent increases. The Company’s leases are primarily accounted for as operating leases. Operating lease ROU assets and short-term and long-term operating lease liabilities are included on the face of the condensed consolidated balance sheet. Finance lease ROU assets are presented within other assets, and finance lease liabilities are presented within accrued

liabilities. In June 2019, the lessors of certain of the Company’s San Francisco offices exercised their right to recapture a portion of the office space, which resulted in a reduction of ROU assets of $18.0 million and a reduction of lease liabilities of $22.5 million for a net benefit to operating lease costs of $4.3 million. In addition, the Company accelerated depreciation of leasehold improvements related to the recaptured office space of $5.2 million. The Company has no leases that have not yet commenced as of September 28, 2019.

Total lease cost consists of the following (in thousands):



	Three Months Ended			Nine Months Ended
	September 28, 2019			September 28, 2019

Finance lease costs:
Amortization of ROU assets	$	989		$	2,640
Interest on lease liabilities	—			—
Operating lease costs⁽¹⁾	5,850			16,834
Variable lease costs	1,463			4,108
Sublease income	(479		)	(4,110		)
Total lease costs	$	7,823		$	19,472

⁽¹⁾ includes short-term leases, which are immaterial.

Supplemental cash flow information related to leases was as follows (in thousands):



	Three Months Ended		Nine Months Ended
	September 28, 2019		September 28, 2019

Cash paid for amounts included in the measurement of lease liabilities:
Financing cash flows from finance leases	$	1,302	$	2,239
Operating cash flows from finance leases	—		—
Operating cash flows from operating leases	6,737		20,775

ROU assets obtained in exchange for lease obligations:
Finance lease liabilities	$	—	—
Operating lease liabilities	—		$	288

Supplemental balance sheet information related to leases was as follows (in thousands):



	September 28, 2019

Finance leases:
Other assets	$	—

Accrued liabilities	$	464

Operating leases:
Operating lease ROU assets	$	71,529

Operating lease liabilities	$	23,313
Long-term operating lease liabilities	70,202
Total operating lease liabilities	$	93,515

Weighted-average lease terms and discount rates are as follows:



	September 28, 2019

Weighted-average remaining lease terms (in years):
Finance leases	0.3
Operating leases	4.4

Weighted-average discount rates:
Finance leases	—%
Operating leases	5.5%

Maturities of lease liabilities as of September 28, 2019 were as follow (in thousands):




	Finance Leases		Operating Leases
Remaining 2019	$	464	$	8,808
2020	—		23,862
2021	—		22,459
2022	—		21,931
2023	—		20,149
Thereafter	—		8,321
Total minimum lease payments	$	464	$	105,530
Less: amount representing interest	—		(12,015		)
Total lease liabilities	$	464	$	93,515

Leases

The Company leases its principal facilities located in San Francisco, California. The Company also leases office space in various locations with expiration dates between 2019 and 2024. The lease agreements often include leasehold improvement incentives, escalating lease payments, renewal provisions and other provisions which require the Company to pay taxes, insurance, maintenance costs or defined rent increases. The Company’s leases are primarily accounted for as operating leases. Operating lease ROU assets and short-term and long-term operating lease liabilities are included on the face of the condensed consolidated balance sheet. Finance lease ROU assets are presented within other assets, and finance lease liabilities are presented within accrued

liabilities. In June 2019, the lessors of certain of the Company’s San Francisco offices exercised their right to recapture a portion of the office space, which resulted in a reduction of ROU assets of $18.0 million and a reduction of lease liabilities of $22.5 million for a net benefit to operating lease costs of $4.3 million. In addition, the Company accelerated depreciation of leasehold improvements related to the recaptured office space of $5.2 million. The Company has no leases that have not yet commenced as of September 28, 2019.

Total lease cost consists of the following (in thousands):



	Three Months Ended			Nine Months Ended
	September 28, 2019			September 28, 2019

Finance lease costs:
Amortization of ROU assets	$	989		$	2,640
Interest on lease liabilities	—			—
Operating lease costs⁽¹⁾	5,850			16,834
Variable lease costs	1,463			4,108
Sublease income	(479		)	(4,110		)
Total lease costs	$	7,823		$	19,472

⁽¹⁾ includes short-term leases, which are immaterial.

Supplemental cash flow information related to leases was as follows (in thousands):



	Three Months Ended		Nine Months Ended
	September 28, 2019		September 28, 2019

Cash paid for amounts included in the measurement of lease liabilities:
Financing cash flows from finance leases	$	1,302	$	2,239
Operating cash flows from finance leases	—		—
Operating cash flows from operating leases	6,737		20,775

ROU assets obtained in exchange for lease obligations:
Finance lease liabilities	$	—	—
Operating lease liabilities	—		$	288

Supplemental balance sheet information related to leases was as follows (in thousands):



	September 28, 2019

Finance leases:
Other assets	$	—

Accrued liabilities	$	464

Operating leases:
Operating lease ROU assets	$	71,529

Operating lease liabilities	$	23,313
Long-term operating lease liabilities	70,202
Total operating lease liabilities	$	93,515

Weighted-average lease terms and discount rates are as follows:



	September 28, 2019

Weighted-average remaining lease terms (in years):
Finance leases	0.3
Operating leases	4.4

Weighted-average discount rates:
Finance leases	—%
Operating leases	5.5%

Maturities of lease liabilities as of September 28, 2019 were as follow (in thousands):




	Finance Leases		Operating Leases
Remaining 2019	$	464	$	8,808
2020	—		23,862
2021	—		22,459
2022	—		21,931
2023	—		20,149
Thereafter	—		8,321
Total minimum lease payments	$	464	$	105,530
Less: amount representing interest	—		(12,015		)
Total lease liabilities	$	464	$	93,515

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 28, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Purchase Commitments The aggregate amount of open purchase orders as of September 28, 2019 was approximately $319.0 million. Of the aggregate amount, $185.0 million related to the Company’s migration to a third-party hosting provider, of which $12.9 million was accrued for as of September 28, 2019. The Company cannot determine the aggregate amount of such purchase orders that represent contractual obligations because purchase orders may represent authorizations to purchase rather than binding agreements. The Company’s purchase orders are based on its current needs and are fulfilled by its suppliers, contract manufacturers, and logistics providers within short periods of time. During the normal course of business, the Company and its contract manufacturers procure components based upon a forecasted production plan. If the Company cancels all or part of the orders, or materially reduces forecasted orders, it may be liable to its suppliers and contract manufacturers for the cost of the excess components purchased by its contract manufacturers. As of September 28, 2019, $19.1 million was accrued for such liabilities to contract manufacturers. Letters of Credit As of September 28, 2019 and December 31, 2018, the Company had outstanding letters of credit of $25.3 million and $36.6 million, respectively, issued to cover the security deposit on the lease of its office headquarters in San Francisco, California, and other facility leases. Legal Proceedings Jawbone. Aliphcom, Inc. d/b/a Jawbone (“Jawbone”) and the Company each initiated civil lawsuits against each other in 2015. These included a complaint filed by Jawbone in California state court alleging the misappropriation of certain trade secrets by six former Jawbone employees who had joined Fitbit and who were also named as defendants. On December 8, 2017, the parties announced the global settlement of all of the outstanding civil litigation on confidential terms, and all of the cases were dismissed with prejudice. On August 12, 2016, the Company was notified by Jawbone that Jawbone had received a confidential subpoena from the U.S. Attorney’s Office for the Northern District of California requesting certain of the Company’s confidential business information that appeared to be related to Jawbone’s allegations of trade secret misappropriation. On February 17, 2017 and February 1, 2018, the Company received subpoenas for documents from the same office. The Company is cooperating with the U.S. Attorney’s Office. On June 14, 2018, the six former Jawbone employees who were named as individual defendants in the state trade secret case were charged in a federal indictment with being in possession of certain Jawbone trade secrets. Sleep Tracking. On May 8, 2015, a purported class action lawsuit was filed against the Company in the U.S. District Court for the Northern District of California, alleging that the sleep tracking function available in certain trackers does not perform as advertised. Plaintiffs sought class certification, restitution, unspecified compensatory and punitive damages, and reasonable costs and expenses including attorneys’ fees. On January 31, 2017, plaintiffs filed a motion for class certification. Plaintiffs’ motion for class certification was granted on November 20, 2017. On April 20, 2017, the Company filed a motion for summary judgment, which the court denied on December 8, 2017. The parties subsequently agreed to a settlement, and on August 1, 2018, the plaintiffs filed a motion for preliminary approval of the class action settlement. At the hearing on September 13, 2018, the court denied preliminary settlement approval without prejudice and ordered revised settlement papers be filed. On November 29, 2018, the court granted preliminary settlement approval and the final approval hearing was scheduled for August 1, 2019. On May 10, 2019, the plaintiffs filed a request for attorneys’ fees. The Company opposed that request. At the final approval hearing, the court indicated that it wanted to see a larger claims rate and asked the parties to submit a re-notice plan. On the fees request, the court offered plaintiffs the option of either having a court-appointed accountant review all of the challenged fees and expenses, or to accept a 90% reduction on those. On August 18, 2019, the plaintiffs filed their fee election, opting for the 90% reduction of challenged fees and expenses. The re-notice plan was approved on October 16, 2019, and new notices have been sent out. The claims deadline is now December 22, 2019. The court has not yet ruled on plaintiff’s fee request. Heart Rate Tracking. On January 6, 2016 and February 16, 2016, two purported class action lawsuits were filed against the Company in the U.S. District Court for the Northern District of California alleging that the PurePulse® heart rate tracking technology does not consistently and accurately record users’ heart rates. Plaintiffs allege common law claims, as well as violations of various states’ false advertising, unfair competition, and consumer protection statutes, and seek class certification, injunctive and declaratory relief, restitution, unspecified compensatory damages, exemplary damages, punitive damages, statutory penalties and damages, and reasonable costs and expenses including attorneys’ fees. On April 15, 2016, the plaintiffs filed a consolidated master class action complaint, and on May 19, 2016, they filed an amended consolidated master class action complaint. On January 9, 2017, the Company filed a motion to compel arbitration. On October 11, 2017, the court granted the motion to compel arbitration. Plaintiffs filed a motion for reconsideration, and that motion was denied on January 24, 2018. On February 20, 2018, a second amended consolidated master class action complaint was filed on behalf of plaintiff Rob Dunn, the only plaintiff not ordered to arbitration, as a purported class action. The complaint alleges the same common law claims as the prior class actions, as well as violations of false advertising, unfair competition, and consumer protection statutes of California and Arizona. The complaint seeks class certification, injunctive and declaratory relief, restitution, unspecified compensatory damages, exemplary damages, punitive damages, statutory penalties and damages, and reasonable costs and expenses including attorneys’ fees. On March 13, 2018, the Company filed a motion to dismiss for failure to state a claim and separately moved to strike the class allegations. The court dismissed the claims for revocation of acceptance, violation of California’s Song-Beverly Consumer Warranty Act, and unjust enrichment, but allowed the remaining claims pending amendment to the complaint with further details. Plaintiff filed a third amended complaint on June 19, 2018. The court granted the Company’s motion to strike and ordered the plaintiff to amend to make clear that he is seeking to represent a class of opt-outs only, but added that plaintiff may amend in the event the Company’s arbitration agreement is found to be unenforceable. On April 3, 2018, the Company received an arbitration demand from Kate McLellan, one of the original plaintiffs who was compelled to arbitration. On July 19, 2019, the parties entered into a settlement of the lawsuit and the arbitration on confidential terms, which are not material to the Company. Securities Litigation I. In 2016, a putative class action was filed in federal court against the Company, certain of its officers and directors, and the underwriters of the Company’s initial public offering alleging violations of the federal securities laws based on alleged materially false and misleading statements about the Company’s PurePulse® heart rate tracking technology. A second putative class action was filed in California state court involving the same statements. The parties agreed to settle the federal and state class actions for $33.3 million, which the Company accrued for as of December 31, 2017. Following court approval of the settlement, the federal and state class action cases were dismissed with prejudice in May 2018. During 2016 and 2017, a total of seven derivative lawsuits were filed in various federal courts and in the Delaware Court of Chancery naming the Company as nominal plaintiff and certain of the Company’s officers and directors as defendants. The federal cases are all stayed. The three cases filed in the Delaware Court of Chancery were consolidated and a second amended complaint was filed in which plaintiffs allege breach of fiduciary duty and insider trading against certain defendants who sold shares in the Company’s initial public offering and/or a secondary offering. On April 26, 2017, the Company filed a motion to dismiss the Delaware cases for failure to state a claim. On December 14, 2018, the court denied the motion to dismiss. The Company filed a motion for interlocutory appeal, which was denied on January 14, 2019. The Company then filed a Notice of Appeal in the Delaware Supreme Court, which was denied on January 30, 2019. The Company believes that the allegations in the derivative lawsuits are without merit and intends to vigorously defend against the claims. Because the Company is in the early stages of these litigation matters, the Company is unable to estimate a reasonably possible loss or range of loss, if any, that may result from these matters. Securities Litigation II. On November 1, 2018, a putative securities class action was filed in the U.S. District Court for the Northern District of California naming the Company and certain of its officers as defendants. The complaint alleges violations of Sections 10(b) and 20 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) arising out of alleged materially false and misleading statements about the Company’s guidance for the fourth quarter of 2016 and full fiscal year 2016 that was provided during the third and fourth quarters of 2016. On November 15, 2018, a second putative securities class action was filed in the same court alleging similar claims against the same defendants. On April 25, 2019, the two actions were consolidated, and a consolidated amended class action complaint was filed on June 24, 2019. The consolidated complaint also alleges violations of Sections 10(b) and 20 of the Exchange Act against the Company and certain officers relating to the Company’s 2016 guidance, on behalf of a putative class of stockholders who purchased Fitbit stock from August 2, 2016 through January 30, 2017. Plaintiffs seek class certification, unspecified compensatory damages, and reasonable costs and expenses including attorneys’ fees. On August 23, 2019, the Company filed a motion to dismiss. The hearing is scheduled for January 8, 2020. The Company believes that the plaintiffs’ allegations are without merit and intends to vigorously defend against the claims. Because the Company is in the early stages of this litigation matter, the Company is unable to estimate a reasonably possible loss or range of loss, if any, that may result from this matter. Philips. On December 4, 2017, Koninklijke Philips N.V. filed a patent infringement suit in Germany in the Regional Court of Mannheim alleging infringement by certain of Fitbit’s products of the German part of EP 1 247 229 B1 (EP229). In October 2018, the case was stayed, pending an appeal of a January 2014 decision by the European Patent Office (EPO) to revoke EP229. On May 31, 2019, the EPO Board of Appeal dismissed the appeal, affirming the decision to revoke EP229. Koninklijke Philips N.V. appealed the EPO Board of Appeal decision on July 30, 2019. On May 30, 2018, Koninklijke Philips N.V. filed a patent infringement suit in the Regional Court of Mannheim alleging infringement by certain of Fitbit’s products of the German part of EP 1 076 806 B1 (EP806). In October 2018, the case was stayed, pending the decision in a parallel nullity proceeding challenging the validity of EP806. On July 22, 2019, Philips North America filed a patent infringement suit in U.S. District Court for the District of Massachusetts alleging infringement of U.S. Patent No. 6,013,007, U.S. Patent No. 7,088,233, U.S. Patent No. 8,277,377, and U.S. Patent No. 6,976,958 by certain of Fitbit’s products. The Company’s response to the complaint is due November 22, 2019. The Company believes that the allegations are without merit and intends to vigorously defend against the claims. Because the Company is in the early stages of these litigation matters, the Company is unable to estimate a reasonably possible loss or range of loss, if any, that may result from these matters. Wynit. In September 2017, Wynit Distribution LLC (“Wynit”) filed for bankruptcy protection under Chapter 11 of the U.S. Bankruptcy Code. Wynit was previously the Company’s largest customer. The Company ceased to recognize revenue from Wynit, which totaled $8.1 million during the third quarter of 2017. Additionally, the Company recorded a charge of $35.8 million during the third quarter of 2017 comprised of cost of revenue of $5.5 million associated with shipments to Wynit in the third quarter of 2017 and bad debt expense of $30.3 million associated with all of Wynit’s outstanding accounts receivables. The Company maintains credit insurance that covers a portion of the exposure related to its customer receivables. The Company recorded an insurance receivable based on an analysis of its insurance policies, including their exclusions, an assessment of the nature of the claim, and information from its insurance carrier. As of September 30, 2017, the Company had recorded an insurance receivable of $26.8 million, included in prepaid expenses and other current assets, associated with the amount it had concluded was probable related to the claim. The $26.8 million insurance receivable allowed the Company to recover $22.7 million of bad debt expense and $4.1 million of cost of revenue, resulting in a net charge of $9.0 million in the consolidated statement of operations comprised of net bad debt expense of $7.6 million and net cost of revenue of $1.4 million. The Company received $21.4 million of the insurance receivable during the fourth quarter of 2017 and the remaining $5.4 million in January 2018. During the nine months ended September 29, 2018, the Company released $12.4 million in product return and rebate reserves related to Wynit, as it believed the possibility of future claims associated with these reserves was remote. This reserve release resulted in a $12.4 million increase in revenue during the nine months ended September 29, 2018. On September 4, 2019, plaintiff Nauni Manty, as the chapter 7 trustee of the bankruptcy estate of Wynit Distribution, LLC, et al, filed a complaint in U.S. Bankruptcy Court in the District of Minnesota. The complaint seeks: (1) avoidance and recovery under 11 U.S.C. §§ 547, 550, and 551 against Fitbit; and (2) avoidance and preservation under 11 U.S.C. §§ 547, 551 of a second lien granted to Fitbit on substantially all the debtors’ assets. The Company believes that the allegations are without merit and intends to vigorously defend against the claims. Because the Company is in the early stages of these litigation matters, the Company is unable to estimate a reasonably possible loss or range of loss, if any, that may result from these matters. Other. The Company is and, from time to time, may in the future become, involved in other legal proceedings in the ordinary course of business. The Company currently believes that the outcome of any of these existing legal proceedings, including the aforementioned cases, either individually or in the aggregate, will not have a material impact on the operating results, financial condition or cash flows of the Company. With respect to existing legal proceedings, the Company has either determined that the existence of a material loss is not reasonably possible or that it is unable to estimate a reasonably possible loss or range of loss. The Company may incur substantial legal fees, which are expensed as incurred, in defending against these legal proceedings. Indemnification In the ordinary course of business, the Company enters into commercial agreements that may include indemnification provisions. Pursuant to such agreements, the Company may indemnify, hold harmless and defend an indemnified party for losses suffered or incurred by the indemnified party. Some of the provisions will limit losses to those arising from third-party actions. In some cases, the indemnification will continue after the termination of the agreement. The maximum potential amount of future payments the Company could be required to make under these provisions is not determinable. To date, the Company has not incurred material costs to defend lawsuits or settle claims related to these indemnification provisions. The Company has also entered into indemnification agreements with its directors and officers that may require the Company to indemnify its directors and officers against liabilities that may arise by reason of their status or service as directors or officers to the fullest extent permitted by Delaware corporate law. The Company also currently has directors’ and officers’ insurance.

Stockholders' Equity

9 Months Ended

Sep. 28, 2019

Share-based Payment Arrangement [Abstract]

Stockholders' Equity

Stockholders’ Equity

Equity Incentive Plans

In May 2015, the Company’s board of directors and stockholders adopted and approved the 2015 Equity Incentive Plan (the “2015 Plan”). The 2015 Plan became effective on June 16, 2015 and serves as the successor to the Amended and Restated 2007 Stock Plan (the “2007 Plan”). The Company ceased granting awards under the 2007 Plan upon the effectiveness of the 2015 Plan. However, any outstanding stock options and restricted stock units (“RSUs”) granted under the 2007 Plan remain subject to the terms of the 2007 Plan. As of September 28, 2019, 26.7 million shares of Class A common stock were reserved and available for future issuance under the 2015 Plan.

Stock Options

Stock option activity under the equity incentive plans was as follows (in thousands, except per share amounts):



	Stock Options Outstanding
	Number of Shares Subject to Stock Options		Weighted– Average Exercise Price		Aggregate Intrinsic Value ⁽¹⁾
Balance—December 31, 2018	16,263		$	3.00
Granted	—		—
Exercised	(817	)	$	1.53
Forfeited or canceled	(62	)	$	5.74
Balance—September 28, 2019	15,384		$	3.07	$	21,357

Stock options vested and expected to vest—September 28, 2019	15,384		$	3.07	$	21,357
Stock options exercisable—September 28, 2019	15,158		$	3.00	$	21,357

⁽¹⁾ The aggregate intrinsic values of stock options outstanding, exercisable, vested and expected to vest as of September 28, 2019 were calculated as the difference between the exercise price of the stock options and the fair value of the Class A common stock of $3.90 as of September 28, 2019.

Restricted Stock Units

RSU activity under the equity incentive plans was as follows (in thousands, except per share amounts):



	RSUs Outstanding		Weighted- Average Grant Date Fair Value
Unvested balance—December 31, 2018	18,376		$	6.69
Granted	11,987		$	5.59
Vested	(8,125	)	$	7.33
Forfeited or canceled	(3,959	)	$	6.56
Unvested balance—September 28, 2019	18,279		$	5.71

In March 2019, the Company issued 0.5 million shares of market-based awards that vest based upon the achievement of a specified stock price. Market conditions were factored into the grant date fair value using a Monte Carlo valuation model, which utilized multiple input variables to determine the probability of the Company achieving the specified stock price targets. Stock-based compensation expense related to these awards will be recognized over the requisite service period regardless of whether the market condition is satisfied, provided that the requisite service period has been completed.

Employee Stock Purchase Plan

In May 2015, the Company’s board of directors adopted the 2015 Employee Stock Purchase Plan (the “2015 ESPP”), which became effective on June 17, 2015. The 2015 ESPP allows eligible employees to purchase shares of the Company’s Class A common stock through payroll deductions at a price per share equal to 85% of the lesser of the fair market value of the Company’s Class A common stock (i) on the first trading day of the applicable offering period and (ii) the last trading day of each purchase period in the applicable offering period. Except for the initial offering period, the 2015 ESPP provides for 6-month offering periods beginning in May and November of each year.

Stock-Based Compensation Expense

Total stock-based compensation expense recognized was as follows (in thousands):



	Three Months Ended				Nine Months Ended
	September 28, 2019		September 29, 2018		September 28, 2019		September 29, 2018
Cost of revenue	$	1,446	$	1,999	$	4,397	$	5,129
Research and development	10,557		14,097		34,437		43,858
Sales and marketing	2,587		3,638		8,900		10,996
General and administrative	3,494		4,381		11,441		13,630
Total stock-based compensation expense	$	18,084	$	24,115	$	59,175	$	73,613

As of September 28, 2019, the total unrecognized stock-based compensation expense related to unvested stock options and RSUs was $94.3 million, which the Company expects to recognize over an estimated weighted average period of 1.9 years.

Income Taxes	9 Months Ended
Income Taxes	Sep. 28, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company is subject to income tax in the United States as well as other tax jurisdictions in which it conducts business. Earnings from non-U.S. activities are subject to local country income tax. For the three and nine months ended September 28, 2019, the Company recorded an expense for income taxes of $1.7 million and $4.0 million, respectively, for an effective tax rate of (3.3)% and (2.0)%, respectively. The effective tax rate for the nine months ended September 28, 2019 was different than the statutory federal tax rate primarily due to the impact of a full valuation allowance on the Company’s U.S. and certain of its foreign deferred tax assets, the mix of income/losses between the Company’s foreign jurisdictions, and pretax losses in jurisdictions for which no tax benefit will be recognized. For the three and nine months ended September 29, 2018, the Company recorded an expense (benefit) for income taxes of $(18.8) million and $4.2 million, for an effective tax rate of 90.2% and (2.1)%, respectively. The effective tax rate for the nine months ended September 29, 2018 was different than the statutory federal tax rate primarily due to the impact of a full valuation allowance on the Company’s U.S. deferred tax assets, the mix of income and losses between the Company’s foreign jurisdictions, and pretax losses in jurisdictions for which no tax benefit will be recognized. Included in this tax amount was a discrete tax benefit of $4.0 million in connection with a fixed assets depreciation tax method change filed with the Company’s 2017 income tax return. On December 22, 2017, the U.S. Tax Cuts and Jobs Act of 2017 (“2017 Tax Act”), was signed into law and includes several key tax provisions that affect the Company, including a reduction of the statutory corporate tax rate from 35% to 21% effective for tax years beginning after December 31, 2017, elimination of the carryback of net operating losses generated after December 31, 2017, and changes to how the United States imposes income tax on multinational corporations, among others. In December 2017, the SEC Staff issued Staff Accounting Bulletin No. 118 (“SAB 118”), Income Tax Accounting Implications of the Tax Cuts and Jobs Act, which allowed the Company to record provisional amounts during a measurement period not to extend beyond one year of the enactment date. As of December 31, 2018, the Company had finalized all provisional amounts related to the 2017 Tax Act. Finalizing provisional adjustments related to the 2017 Tax Act did not have a material impact on the Company’s consolidated financial statements for the year ended December 31, 2018. On June 7, 2019, the U.S. Court of Appeals for the Ninth Circuit issued an opinion in Altera Corp. v. Commissioner upholding the U.S. Treasury Department’s regulations requiring related parties in an intercompany cost-sharing arrangement to share expenses related to share-based compensation in proportion to the economic activity of the related parties. This opinion reversed the prior decision of the U.S. Tax Court. On July 23, 2019, Altera Corp. petitioned the Ninth Circuit Court of Appeals for an en banc rehearing of the Ninth Circuit’s previous decision on June 7, 2019. Since the Ninth Circuit ruling is potentially subject to further judicial review, the Company will continue to monitor developments and potential impacts to our consolidated financial statements. The Company accounts for deferred taxes under ASC Topic 740, “Income Taxes,” which involves weighing positive and negative evidence concerning the realizability of the Company’s deferred tax assets in each jurisdiction. In evaluating its ability to realize the net deferred tax assets, the Company considered all available positive and negative evidence, including its past operating results and the forecast of future market growth, forecasted earnings, future taxable income, and prudent and feasible tax planning strategies. As of September 28, 2019, the Company maintains a valuation allowance against all its U.S. deferred tax assets and against certain of its foreign deferred tax assets. The Company will continue to assess the realizability of its deferred tax assets in each of the applicable jurisdictions going forward. As of September 28, 2019, the total amount of gross unrecognized tax benefits was $47.9 million, of which $25.8 million would affect the effective tax rate if recognized. The Company did not have any tax positions as of September 28, 2019 for which it is reasonably possible that the total amount of gross unrecognized tax benefits will increase or decrease within the following 12 months.

Net Loss per Share

9 Months Ended

Sep. 28, 2019

Earnings Per Share [Abstract]

Net Loss per Share

The following table sets forth the computation of the Company’s basic and diluted net loss per share (in thousands, except per share amounts):



	Three Months Ended						Nine Months Ended
	September 28, 2019			September 29, 2018			September 28, 2019			September 29, 2018
Numerator:
Net loss	$	(51,893	)	$	(2,056	)	$	(199,876	)	$	(201,201	)

Denominator:
Weighted-average shares of common stock—basic for Class A and Class B	258,753			245,838			256,046			242,746
Effect of dilutive securities	—			—			—			—
Weighted-average shares of common stock—diluted for Class A and Class B	258,753			245,838			256,046			242,746
Net loss per share:
Basic	$	(0.20	)	$	(0.01	)	$	(0.78	)	$	(0.83	)
Diluted	$	(0.20	)	$	(0.01	)	$	(0.78	)	$	(0.83	)

The following potentially dilutive common shares were excluded from the computation of diluted net loss per share for the periods presented because including them would have been anti-dilutive (in thousands):



	Three Months Ended		Nine Months Ended
	September 28, 2019	September 29, 2018	September 28, 2019	September 29, 2018

Stock options to purchase common stock	15,384	11,982	15,584	12,150
RSUs	18,279	8,123	20,998	8,607
Warrant	230	230	230	230
Diluted impact of ESPP	1,412	191	1,351	177
Total	35,305	20,526	38,163	21,164

Significant Customer Information and Other Information

9 Months Ended

Sep. 28, 2019

Risks and Uncertainties [Abstract]

Significant Customer Information and Other Information

Retailer and Distributor Concentration

Retailers and distributors that accounted for equal to or greater than 10% of total revenue for the three months ended September 28, 2019 and September 29, 2018 were as follows:



	Three Months Ended				Nine Months Ended
	September 28, 2019		September 29, 2018		September 28, 2019	September 29, 2018
G	12	%	10	%	*	*
D	11	%	13	%	*	*
C	*		12	%	*	10	%

* Represents less than 10%.

Retailers and distributors that accounted for equal to or greater than 10% of accounts receivable at September 28, 2019 and December 31, 2018 were as follows:



	September 28, 2019		December 31, 2018
G	15	%	*
D	13		10	%
C	10		12
B	*		16
E	*		11
F	*		10

* Represents less than 10%.

Geographic and Other Information

Revenue by geographic region, based on ship-to destinations, was as follows (in thousands):



	Three Months Ended				Nine Months Ended
	September 28, 2019		September 29, 2018		September 28, 2019		September 29, 2018
United States	$	206,654	$	230,171	$	522,607	$	552,118
Americas excluding United States	16,722		24,799		51,227		56,737
Europe, Middle East, and Africa	82,951		104,186		257,612		234,693
APAC	40,873		34,419		101,200		97,236
Total	$	347,200	$	393,575	$	932,646	$	940,784

As of September 28, 2019 and December 31, 2018, long-lived assets, which represent property and equipment, located outside the United States were $30.6 million and $36.9 million, respectively.

Acquisitions	9 Months Ended
Acquisitions	Sep. 28, 2019
Business Combinations [Abstract]
Acquisitions	Acquisitions 2018 Acquisition In February 2018, the Company completed a purchase of Twine Health, Inc., a privately-held company, which was accounted for as a business combination, for total purchase price consideration of $16.7 million, of which $5.4 million was allocated to developed technology intangible assets, $3.8 million to customer relationships intangible asset, $9.9 million to goodwill, $1.7 million to deferred tax liabilities, $0.2 million to deferred revenue, and $0.6 million to net assumed liabilities. Approximately $2.6 million of the consideration payable to Twine Health, Inc. was held as partial security for certain indemnification obligations, which was paid in August 2019. The acquisition is expected to extend the Company’s reach into healthcare and lay the foundation to expand its offerings to health plans, health systems and self-insured employers, while creating opportunities to increase subscription-based revenue. The amortization periods of the acquired developed technology and customer relationships are approximately four years and seven years, respectively. Goodwill is not deductible for tax purposes.

Subsequent Events	9 Months Ended
Subsequent Events	Sep. 28, 2019
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events In October 2019, the Company acquired a privately-held company for total consideration of $6.0 million, which includes contingent consideration of up to $2.2 million. This acquisition is to be accounted for as a business combination. Management is currently evaluating the purchase price allocation for this transaction. In November 2019, the Company announced that it had entered into an Agreement and Plan of Merger (the “Merger Agreement”) with Google LLC, a Delaware limited liability company (“Google”) and Magnoliophyta Inc., a Delaware corporation and wholly owned subsidiary of Google (the “Merger Sub”). Pursuant to the terms of, and subject to the conditions specified in, the Merger Agreement, the Merger Sub will merge with and into the Company, and the Company will become a wholly owned subsidiary of Google (the “Merger”). If the Merger is completed, Google will acquire all the shares of the Company’s Class A common stock and Class B common stock (together, the “Shares”) for $7.35 per share in cash, without interest (the “Merger Consideration”). All Shares underlying vested stock options and vested stock-based awards will be converted into the right to receive the Merger Consideration (or, in the case of stock options, the difference between the Merger Consideration and the applicable per share exercise price), less any applicable tax withholdings. Unvested stock options and stock-based awards will generally be converted into cash-based awards with an equivalent value based on the Merger Consideration and vesting schedule. The Merger is expected to close in 2020, subject to customary closing conditions, including approval by the Company’s stockholders, the expiration or termination of any waiting periods or receipt of any requisite consents under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, and approval under the antitrust laws of the European Union and other jurisdictions agreed by the parties and satisfaction of other closing conditions.

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 28, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	The accompanying condensed consolidated financial statements of Fitbit, Inc. (the “Company”) are unaudited. The condensed consolidated balance sheet at December 31, 2018 has been derived from the audited financial statements of the Company. The accompanying condensed financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) for interim financial information, and in management’s opinion, includes all adjustments, consisting of only normal recurring adjustments, necessary for the fair statement of the Company’s financial position, its results of operations, and cash flows for the interim periods presented. The results of operations for the nine months ended September 28, 2019 are not necessarily indicative of the results to be expected for the full fiscal year or any other period. The accompanying condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2018, filed with the Securities and Exchange Commission (“SEC”) on March 1, 2019. The Company’s fiscal year ends on December 31 of each year. The Company is on a 4-4-5 week quarterly calendar. There were 91 days in each of the three months ended September 28, 2019 and September 29, 2018, respectivel
Principles of Consolidation	The condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated.
Use of Estimates	Use of Estimates The preparation of condensed consolidated financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported and disclosed in the condensed consolidated financial statements and accompanying notes. The primary estimates and assumptions made by management are related to revenue recognition, reserves for sales returns and incentives, reserves for warranty, valuation of stock-based awards, fair value of derivative assets and liabilities, allowance for doubtful accounts, inventory valuation, fair value of goodwill and acquired tangible and intangible assets and liabilities assumed during acquisitions, the recoverability of intangible assets and their useful lives, contingencies, income taxes, and impairment of an equity investment. Actual results could differ from those estimates, and such differences may be material to the condensed consolidated financial statements.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Accounting Pronouncements Not Yet Adopted In June 2016, the Financial Accounting Standards Board (the “FASB”) issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. ASU 2016-13 provides for a new impairment model which requires measurement and recognition of expected credit losses for most financial assets and certain other instruments, including but not limited to accounts receivable and available for sale debt securities. In May 2019, the FASB issued ASU 2019-05, Financial Instruments-Credit Losses (Topic 326): Targeted Transition Relief. This ASU provides an option to irrevocably elect to measure certain individual financial assets at fair value instead of amortized cost. ASU 2016-13 and ASU 2019-05 will become effective for the Company on January 1, 2020 and early adoption is permitted. The Company is currently evaluating the impact of this guidance on its consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment. ASU 2017-04 simplifies the subsequent measurement of goodwill by eliminating the second step of the goodwill impairment test. The second step measures a goodwill impairment loss by comparing the implied fair value of a reporting unit’s goodwill with the carrying amount of that goodwill. Under ASU 2017-04, a company will record an impairment charge based on the excess of a reporting unit’s carrying amount over its fair value. ASU 2017-04 will be applied prospectively and is effective for annual or interim goodwill impairment tests in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company does not expect adoption of this guidance will have a material impact on its consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement. ASU 2018-13 modifies the disclosure requirements on fair value measurements and will become effective for the Company on January 1, 2020 and early adoption is permitted. The Company is currently evaluating the impact of this guidance on its consolidated financial statements. In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. ASU 2018-15 clarifies the accounting for implementation costs in cloud computing arrangements and will become effective for the Company on January 1, 2020 and early adoption is permitted. The Company is currently evaluating the impact of this guidance on its consolidated financial statements. In April 2019, the FASB issued ASU No. 2019-04, Codification Improvements to Topic 326, Financial Instruments – Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments. This ASU clarifies and corrects guidance related to Topic 326, Topic 815, and Topic 825. The applicable provisions of this ASU will become effective for the Company on January 1, 2020. The Company is currently evaluating the impact of this guidance on its consolidated financial statements. Accounting Pronouncements Recently Adopted In February 2016, the FASB issued ASU 2016-02, Leases and subsequent amendments to the initial guidance; ASU 2017-13, ASU 2018-10 and ASU 2018-11 (collectively, “Topic 842”). Topic 842 requires lessees to recognize ROU assets and lease liabilities for operating leases, initially measured at the present value of the lease payments, on the balance sheet. The Company adopted the standard effective January 1, 2019 using a modified retrospective approach. Prior periods were not retrospectively adjusted. The cumulative effect upon adoption on the opening accumulated deficit balance was zero. The Company elected the available practical expedients, which allowed for carryforward of historical assessments of whether contracts contain or are leases, historical lease classification, and remaining lease terms. The standard had a material impact on the Company’s condensed consolidated balance sheets but did not have an impact on its condensed consolidated statements of operations. The most significant impact was the recognition of ROU assets and short-term and long-term lease liabilities for operating leases. The balances of operating lease ROU assets, operating lease liabilities, and long-term operating lease liabilities as of September 28, 2019 were $71.5 million, $23.3 million, and $70.2 million, respectively. The impact to other financial statement line items was immaterial. Adoption of the standard had no impact to net cash from or used in operating, investing, or financing activities in the Company’s consolidated statement of cash flows. Refer to Note 5 for further information on leases. In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities. ASU 2017-12 amends the hedge accounting rules to simplify the application of hedge accounting standard and better portray the economic results of risk management activities in the financial statements. The standard expands the ability to hedge non-financial and financial risk components, reduces complexity in fair value hedges of interest rate risk, eliminates the requirement to separately measure and report hedge ineffectiveness, as well as eases certain hedge effectiveness assessment requirements. ASU 2017-12 became effective for the Company on January 1, 2019 with early adoption permitted. The Company early adopted this new standard in the first quarter of 2018. The adoption of this standard did not have a material impact on the Company’s consolidated financial statements. In June 2018, the FASB issued ASU 2018-07, Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting. ASU 2018-07 expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. ASU 2018-07 became effective for the Company on January 1, 2019. The adoption of this standard did not have a material impact on the Company’s consolidated financial statements.

Fair Value Measurements (Tables)

9 Months Ended

Sep. 28, 2019

Fair Value Disclosures [Abstract]

Schedule of fair value of assets and liabilities measured on recurring basis

The following tables set forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands):



	September 28, 2019
	Level 1		Level 2		Level 3		Total

Assets:
Money market funds	$	95,079	$	—	$	—	$	95,079
U.S. government agencies	—		83,246		—		83,246
Corporate debt securities	—		222,823		—		222,823
Derivative assets	—		775		—		775
Total	$	95,079	$	306,844	$	—	$	401,923
Liabilities:
Derivative liabilities	$	—	$	9	$	—	$	9
Total	$	—	$	9	$	—	$	9



	December 31, 2018
	Level 1		Level 2		Level 3		Total

Assets:
Money market funds	$	273,546	$	—	$	—	$	273,546
U.S. government agencies	—		72,840		—		72,840
Corporate debt securities	—		228,953		—		228,953
Derivative assets	—		623		—		623
Total	$	273,546	$	302,416	$	—	$	575,962
Liabilities:
Derivative liabilities	$	—	$	549	$	—	$	549
Stock warrant liability	—		—		410		410
Total	$	—	$	549	$	410	$	959

Financial Instruments (Tables)

9 Months Ended

Sep. 28, 2019

Investments, Debt and Equity Securities [Abstract]

Schedule of cash, cash equivalents and marketable securities

The following table classifies marketable securities by contractual maturities (in thousands):



	September 28, 2019		December 31, 2018

Due in one year	$	205,923	$	249,493
Due in one to two years	8,894		—
Total	$	214,817	$	249,493

The following table sets forth cash, cash equivalents and marketable securities as of September 28, 2019 (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Cash and Cash Equivalents		Marketable Securities

Cash	$	101,100	$	—	$	—		$	101,100	$	101,100	$	—
Money market funds	95,079		—		—			95,079		95,079		—
U.S. government agencies	83,190		61		(5		)	83,246		18,232		65,014
Corporate debt securities	222,712		124		(13		)	222,823		73,020		149,803
Total	$	502,081	$	185	$	(18	)	$	502,248	$	287,431	$	214,817

The following table sets forth cash, cash equivalents and marketable securities as of December 31, 2018 (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Cash and Cash Equivalents		Marketable Securities

Cash	$	148,110	$	—	$	—		$	148,110	$	148,110	$	—
Money market funds	273,546		—		—			273,546		273,546		—
U.S. government agencies	72,884		1		(45		)	72,840		9,738		63,102
Corporate debt securities	229,040		—		(87		)	228,953		42,562		186,391
Total	$	723,580	$	1	$	(132	)	$	723,449	$	473,956	$	249,493

Schedule of derivative instruments in statement of financial position, fair value

The following table presents the fair value of the Company’s foreign currency derivative contracts as of the periods presented (in thousands):



		September 28, 2019				December 31, 2018
	Balance Sheet Location	Fair Value Derivative Assets		Fair Value Derivative Liabilities		Fair Value Derivative Assets		Fair Value Derivative Liabilities

Hedges not designated	Prepaid expenses and other current assets	$	775	$	—	$	623	$	—
Hedges not designated	Accrued liabilities	—		9		—		549
Total fair value of derivative instruments		$	775	$	9	$	623	$	549

Schedule of cash flow hedging instruments, statement of operations

The following table presents the pre-tax impact of the Company’s foreign currency derivative contracts on other comprehensive income (“OCI”) and the condensed consolidated statements of operations for the periods presented (in thousands):



		Three Months Ended				Nine Months Ended
	Income Statement Location	September 28, 2019		September 29, 2018		September 28, 2019		September 29, 2018

Foreign exchange cash flow hedges:
Gain recognized in OCI – effective portion		$	—	$	911	$	—	$	7,489
Gain reclassified from OCI into income – effective portion	Revenue	—		2,449		—		3,606

Foreign exchange balance sheet hedges:
Gain recognized in income	Other income, net	$	2,041	$	1,035	$	1,567	$	3,335

Schedule of cash flow hedging instruments, comprehensive income

The following table presents the pre-tax impact of the Company’s foreign currency derivative contracts on other comprehensive income (“OCI”) and the condensed consolidated statements of operations for the periods presented (in thousands):



		Three Months Ended				Nine Months Ended
	Income Statement Location	September 28, 2019		September 29, 2018		September 28, 2019		September 29, 2018

Foreign exchange cash flow hedges:
Gain recognized in OCI – effective portion		$	—	$	911	$	—	$	7,489
Gain reclassified from OCI into income – effective portion	Revenue	—		2,449		—		3,606

Foreign exchange balance sheet hedges:
Gain recognized in income	Other income, net	$	2,041	$	1,035	$	1,567	$	3,335

Schedule of derivative contracts on consolidated statement of operations

The following table provides the location in the condensed consolidated statements of operations and amount of the recognized gains or losses to the Company’s derivative instruments designated as hedging instruments (in thousands):



	Three Months Ended				Nine Months Ended
	September 28, 2019		September 29, 2018		September 28, 2019		September 29, 2018

Total amounts presented in the condensed consolidated statement of operations in which the effects of cash flow hedges are recorded in revenue	$	347,200	$	393,575	$	932,646	$	940,784
Total amounts presented in the condensed consolidated statement of operations in which the effects of cash flow hedges are recorded in operating expenses	160,072		171,328		511,263		586,907
Gains on foreign exchange contracts designated as cash flow hedges reclassified from OCI into revenue	—		2,449		—		3,606

Schedule of offsetting of foreign currency derivative contracts

The following tables set forth the available offsetting of net derivative assets under the master netting arrangements as of September 28, 2019 and December 31, 2018 (in thousands):



	September 28, 2019
	Gross Amounts Offset in the Condensed Consolidated Balance Sheets						Gross Amounts Not Offset in Condensed Consolidated Balance Sheets
	Gross Amounts Recognized		Gross Amounts Offset		Net Amounts Presented		Financial Instruments		Cash Collateral Received		Net Amount

Foreign exchange contracts assets	$	775	$	—	$	775	$	9	$	—	$	766
Foreign exchange contracts liabilities	9		—		9		9		—		—

	December 31, 2018
	Gross Amounts Offset in the Condensed Consolidated Balance Sheets						Gross Amounts Not Offset in Condensed Consolidated Balance Sheets
	Gross Amounts Recognized		Gross Amounts Offset		Net Amounts Presented		Financial Instruments		Cash Collateral Received		Net Amount

Foreign exchange contracts assets	$	623	$	—	$	623	$	549	$	—	$	74
Foreign exchange contracts liabilities	549		—		549		549		—		—

- Definition

Tabular disclosure of pertinent information about a derivative or group of derivatives on a disaggregated basis, such as for individual instruments, or small groups of similar instruments. May include a combination of the type of instrument, risks being hedged, notional amount, hedge designation, related hedged item, inception date, maturity date, or other relevant item.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109980867&loc=d3e41620-113959

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=109980867&loc=d3e41638-113959

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109980867&loc=d3e41678-113959

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109980867&loc=d3e41641-113959

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(n)(2))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579240-113959

+ Details

Balance Sheet Components (Tables)

9 Months Ended

Sep. 28, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of deferred revenue

Changes in the total short-term and long-term deferred revenue balances were as follows (in thousands):



	Three Months Ended			Nine Months Ended
	September 28, 2019			September 28, 2019

Beginning balances	$	33,361		$	36,836
Deferral of revenue	10,515			27,325
Recognition of deferred revenue	(9,626		)	(29,911		)
Ending balances	$	34,250		$	34,250

Schedule of accounts receivable reserves

Revenue returns reserve activities were as follows (in thousands):



	Three Months Ended						Nine Months Ended
	September 28, 2019			September 29, 2018			September 28, 2019			September 29, 2018

Beginning balances	$	75,044		$	74,996		$	104,001		$	109,872
Increases ⁽¹⁾	41,945			43,383			119,070			106,385
Returns taken	(42,845		)	(39,862		)	(148,927		)	(137,740		)
Ending balances	$	74,144		$	78,517		$	74,144		$	78,517


⁽¹⁾	Increases in the revenue returns reserve include provisions for open box returns and stock rotations.

Schedule of inventories

Inventories consisted of the following (in thousands):



	September 28, 2019		December 31, 2018

Components	$	6,504	$	8,866
Finished goods	238,592		116,005
Total inventories	$	245,096	$	124,871

Schedule of prepaid expenses and other current asset

Prepaid expenses and other current assets consisted of the following (in thousands):



	September 28, 2019		December 31, 2018

Prepaid expenses	$	10,841	$	18,100
Point-of-purchase (“POP”) displays, net	3,467		5,143
Prepaid marketing	2,941		3,258
Derivative asset	775		623
Other	15,352		15,201
Total prepaid expenses and other current assets	$	33,376	$	42,325

Schedule of property and equipment

Property and equipment, net, consisted of the following (in thousands):




	September 28, 2019			December 31, 2018

Tooling and manufacturing equipment	$	98,773		$	80,685
Furniture and office equipment	20,015			22,738
Purchased and internally-developed software	26,634			21,741
Leasehold improvements	59,741			67,715
Total property and equipment	205,163			192,879
Less: Accumulated depreciation and amortization	(116,931		)	(86,593		)
Property and equipment, net	$	88,232		$	106,286

Schedule of intangible assets (excluding goodwill)

The carrying amounts of the intangible assets as of September 28, 2019 and December 31, 2018 were as follows (in thousands):



	September 28, 2019							December 31, 2018
	Gross		Accumulated Amortization			Net		Gross		Accumulated Amortization			Net

Developed technology	$	35,988	$	(21,506	)	$	14,482	$	35,988	$	(15,983	)	$	20,005
Customer relationships	3,790		(857		)	2,933		3,790		(451		)	3,339
Trademarks and other	1,278		(1,174		)	104		1,278		(1,002		)	276
Total intangible assets, net	$	41,056	$	(23,537	)	$	17,519	$	41,056	$	(17,436	)	$	23,620

Schedule of estimated future amortization expense

The estimated future amortization expense of acquired finite-lived intangible assets to be charged to cost of revenue and operating expenses after September 28, 2019 is as follows (in thousands):



	Cost of Revenue		Operating Expenses		Total

Remaining 2019	$	2,392	$	207	$	2,599
2020	6,192		643		6,835
2021	4,504		597		5,101
2022	955		597		1,552
2023	—		597		597
Thereafter	—		835		835
Total finite-lived intangible assets, net	$	14,043	$	3,476	$	17,519

Schedule of accrued liabilities

Accrued liabilities consisted of the following (in thousands):



	September 28, 2019		December 31, 2018
	September 28, 2019		December 31, 2018
Accrued sales incentives	$	92,087	$	126,400
Accrued revenue reserve from returns	74,144		104,001
Product warranty	44,904		45,605
Accrued manufacturing expense and freight	36,952		21,357
Accrued sales and marketing	29,725		18,171
Accrued co-op advertising and marketing development funds	27,783		30,435
Accrued research and development	16,521		8,783
Sales taxes and VAT payable	14,108		20,121
Employee-related liabilities	13,513		33,916
Inventory received but not billed	4,397		6,373
Accrued legal settlements and fees	3,375		2,821
Finance lease liabilities	464		—
Derivative liabilities	9		549
Other	7,830		18,702
Accrued liabilities	$	365,812	$	437,234

Schedule of product warranty reserves

Product warranty reserve activities were as follows (in thousands):



	Three Months Ended						Nine Months Ended
	September 28, 2019			September 29, 2018			September 28, 2019			September 29, 2018

Beginning balances	$	45,260		$	50,468		$	45,605		$	87,882
Charged to cost of revenue	11,019			9,245			28,247			(1,722		)
Changes related to pre-existing warranties	2,201			(1,354		)	4,874			(9,226		)
Settlement of claims	(13,576		)	(10,504		)	(33,822		)	(29,079		)
Ending balances	$	44,904		$	47,855		$	44,904		$	47,855

Schedule of accumulated other comprehensive income

The components and activity of accumulated other comprehensive income (“AOCI”), net of tax, were as follows (in thousands):



	Unrealized Gains (Losses) on Cash Flow Hedges			Currency Translation Adjustments		Unrealized Gains (Losses) on Available-for-Sale Investments			Total

Balance at December 31, 2018	$	66		$	—	$	(132	)	$	(66	)
Other comprehensive income (loss) before reclassifications	(66		)	—		364			298
Other comprehensive income (loss)	(66		)	—		364			298
Balance at September 28, 2019	$	—		$	—	$	232		$	232

Leases (Tables)

9 Months Ended

Sep. 28, 2019

Leases [Abstract]

Lease, Cost

Total lease cost consists of the following (in thousands):



	Three Months Ended			Nine Months Ended
	September 28, 2019			September 28, 2019

Finance lease costs:
Amortization of ROU assets	$	989		$	2,640
Interest on lease liabilities	—			—
Operating lease costs⁽¹⁾	5,850			16,834
Variable lease costs	1,463			4,108
Sublease income	(479		)	(4,110		)
Total lease costs	$	7,823		$	19,472

⁽¹⁾ includes short-term leases, which are immaterial.

Supplemental cash flow information related to leases was as follows (in thousands):



	Three Months Ended		Nine Months Ended
	September 28, 2019		September 28, 2019

Cash paid for amounts included in the measurement of lease liabilities:
Financing cash flows from finance leases	$	1,302	$	2,239
Operating cash flows from finance leases	—		—
Operating cash flows from operating leases	6,737		20,775

ROU assets obtained in exchange for lease obligations:
Finance lease liabilities	$	—	—
Operating lease liabilities	—		$	288

Assets And Liabilities, Lessee

Supplemental balance sheet information related to leases was as follows (in thousands):



	September 28, 2019

Finance leases:
Other assets	$	—

Accrued liabilities	$	464

Operating leases:
Operating lease ROU assets	$	71,529

Operating lease liabilities	$	23,313
Long-term operating lease liabilities	70,202
Total operating lease liabilities	$	93,515

Schedule of Weighted-Average Lease Terms and Discount Rates

Weighted-average lease terms and discount rates are as follows:



	September 28, 2019

Weighted-average remaining lease terms (in years):
Finance leases	0.3
Operating leases	4.4

Weighted-average discount rates:
Finance leases	—%
Operating leases	5.5%

Lessee, Operating Lease, Liability, Maturity

Maturities of lease liabilities as of September 28, 2019 were as follow (in thousands):




	Finance Leases		Operating Leases
Remaining 2019	$	464	$	8,808
2020	—		23,862
2021	—		22,459
2022	—		21,931
2023	—		20,149
Thereafter	—		8,321
Total minimum lease payments	$	464	$	105,530
Less: amount representing interest	—		(12,015		)
Total lease liabilities	$	464	$	93,515

Finance Lease, Liability, Maturity

Maturities of lease liabilities as of September 28, 2019 were as follow (in thousands):




	Finance Leases		Operating Leases
Remaining 2019	$	464	$	8,808
2020	—		23,862
2021	—		22,459
2022	—		21,931
2023	—		20,149
Thereafter	—		8,321
Total minimum lease payments	$	464	$	105,530
Less: amount representing interest	—		(12,015		)
Total lease liabilities	$	464	$	93,515

Stockholders' Equity (Tables)

9 Months Ended

Sep. 28, 2019

Share-based Payment Arrangement [Abstract]

Schedule of stock option activity

Stock option activity under the equity incentive plans was as follows (in thousands, except per share amounts):



	Stock Options Outstanding
	Number of Shares Subject to Stock Options		Weighted– Average Exercise Price		Aggregate Intrinsic Value ⁽¹⁾
Balance—December 31, 2018	16,263		$	3.00
Granted	—		—
Exercised	(817	)	$	1.53
Forfeited or canceled	(62	)	$	5.74
Balance—September 28, 2019	15,384		$	3.07	$	21,357

Stock options vested and expected to vest—September 28, 2019	15,384		$	3.07	$	21,357
Stock options exercisable—September 28, 2019	15,158		$	3.00	$	21,357

⁽¹⁾ The aggregate intrinsic values of stock options outstanding, exercisable, vested and expected to vest as of September 28, 2019 were calculated as the difference between the exercise price of the stock options and the fair value of the Class A common stock of $3.90 as of September 28, 2019.

Schedule of restricted stock unit activity

RSU activity under the equity incentive plans was as follows (in thousands, except per share amounts):



	RSUs Outstanding		Weighted- Average Grant Date Fair Value
Unvested balance—December 31, 2018	18,376		$	6.69
Granted	11,987		$	5.59
Vested	(8,125	)	$	7.33
Forfeited or canceled	(3,959	)	$	6.56
Unvested balance—September 28, 2019	18,279		$	5.71

Schedule of stock-based compensation expense

Total stock-based compensation expense recognized was as follows (in thousands):



	Three Months Ended				Nine Months Ended
	September 28, 2019		September 29, 2018		September 28, 2019		September 29, 2018
Cost of revenue	$	1,446	$	1,999	$	4,397	$	5,129
Research and development	10,557		14,097		34,437		43,858
Sales and marketing	2,587		3,638		8,900		10,996
General and administrative	3,494		4,381		11,441		13,630
Total stock-based compensation expense	$	18,084	$	24,115	$	59,175	$	73,613

Net Loss per Share (Tables)

9 Months Ended

Sep. 28, 2019

Earnings Per Share [Abstract]

Schedule of basic and diluted net loss per share

The following table sets forth the computation of the Company’s basic and diluted net loss per share (in thousands, except per share amounts):



	Three Months Ended						Nine Months Ended
	September 28, 2019			September 29, 2018			September 28, 2019			September 29, 2018
Numerator:
Net loss	$	(51,893	)	$	(2,056	)	$	(199,876	)	$	(201,201	)

Denominator:
Weighted-average shares of common stock—basic for Class A and Class B	258,753			245,838			256,046			242,746
Effect of dilutive securities	—			—			—			—
Weighted-average shares of common stock—diluted for Class A and Class B	258,753			245,838			256,046			242,746
Net loss per share:
Basic	$	(0.20	)	$	(0.01	)	$	(0.78	)	$	(0.83	)
Diluted	$	(0.20	)	$	(0.01	)	$	(0.78	)	$	(0.83	)

Schedule of antidilutive securities excluded from earnings per share

The following potentially dilutive common shares were excluded from the computation of diluted net loss per share for the periods presented because including them would have been anti-dilutive (in thousands):



	Three Months Ended		Nine Months Ended
	September 28, 2019	September 29, 2018	September 28, 2019	September 29, 2018

Stock options to purchase common stock	15,384	11,982	15,584	12,150
RSUs	18,279	8,123	20,998	8,607
Warrant	230	230	230	230
Diluted impact of ESPP	1,412	191	1,351	177
Total	35,305	20,526	38,163	21,164

Significant Customer Information and Other Information (Tables)

9 Months Ended

Sep. 28, 2019

Risks and Uncertainties [Abstract]

Schedules of concentration of risk

Revenue by geographic region, based on ship-to destinations, was as follows (in thousands):



	Three Months Ended				Nine Months Ended
	September 28, 2019		September 29, 2018		September 28, 2019		September 29, 2018
United States	$	206,654	$	230,171	$	522,607	$	552,118
Americas excluding United States	16,722		24,799		51,227		56,737
Europe, Middle East, and Africa	82,951		104,186		257,612		234,693
APAC	40,873		34,419		101,200		97,236
Total	$	347,200	$	393,575	$	932,646	$	940,784

Retailers and distributors that accounted for equal to or greater than 10% of accounts receivable at September 28, 2019 and December 31, 2018 were as follows:



	September 28, 2019		December 31, 2018
G	15	%	*
D	13		10	%
C	10		12
B	*		16
E	*		11
F	*		10

* Represents less than 10%.

Retailers and distributors that accounted for equal to or greater than 10% of total revenue for the three months ended September 28, 2019 and September 29, 2018 were as follows:



	Three Months Ended				Nine Months Ended
	September 28, 2019		September 29, 2018		September 28, 2019	September 29, 2018
G	12	%	10	%	*	*
D	11	%	13	%	*	*
C	*		12	%	*	10	%

* Represents less than 10%.

Basis of Presentation and Summary of Significant Accounting Policies - Accounting Pronouncements Recently Adopted (Details) $ in Thousands	Sep. 28, 2019 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Operating lease right-of-use assets	$ 71,529
Operating lease liabilities	23,313
Long-term operating lease liabilities	$ 70,202

Fair Value Measurements (Details) - USD ($)	3 Months Ended		9 Months Ended
Fair Value Measurements (Details) - USD ($)	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018	Dec. 31, 2018
Assets:
Available for sale securities	$ 502,248,000		$ 502,248,000		$ 723,449,000
Liabilities:
Transfers between fair value levels	0	$ 0	0	$ 0
U.S. government agencies
Assets:
Available for sale securities	83,246,000		83,246,000		72,840,000
Corporate debt securities
Assets:
Available for sale securities	222,823,000		222,823,000		228,953,000
Fair Value, Recurring
Assets:
Money market funds	95,079,000		95,079,000		273,546,000
Derivative assets	775,000		775,000		623,000
Total	401,923,000		401,923,000		575,962,000
Liabilities:
Derivative liabilities	9,000		9,000		549,000
Stock warrant liability					410,000
Total	9,000		9,000		959,000
Fair Value, Recurring \| U.S. government agencies
Assets:
Available for sale securities	83,246,000		83,246,000		72,840,000
Fair Value, Recurring \| Corporate debt securities
Assets:
Available for sale securities	222,823,000		222,823,000		228,953,000
Fair Value, Recurring \| Level 1
Assets:
Money market funds	95,079,000		95,079,000		273,546,000
Derivative assets	0		0		0
Total	95,079,000		95,079,000		273,546,000
Liabilities:
Derivative liabilities	0		0		0
Stock warrant liability					0
Total	0		0		0
Fair Value, Recurring \| Level 1 \| U.S. government agencies
Assets:
Available for sale securities	0		0		0
Fair Value, Recurring \| Level 1 \| Corporate debt securities
Assets:
Available for sale securities	0		0		0
Fair Value, Recurring \| Level 2
Assets:
Money market funds	0		0		0
Derivative assets	775,000		775,000		623,000
Total	306,844,000		306,844,000		302,416,000
Liabilities:
Derivative liabilities	9,000		9,000		549,000
Stock warrant liability					0
Total	9,000		9,000		549,000
Fair Value, Recurring \| Level 2 \| U.S. government agencies
Assets:
Available for sale securities	83,246,000		83,246,000		72,840,000
Fair Value, Recurring \| Level 2 \| Corporate debt securities
Assets:
Available for sale securities	222,823,000		222,823,000		228,953,000
Fair Value, Recurring \| Level 3
Assets:
Money market funds	0		0		0
Derivative assets	0		0		0
Total	0		0		0
Liabilities:
Derivative liabilities	0		0		0
Stock warrant liability					410,000
Total	0		0		410,000
Fair Value, Recurring \| Level 3 \| U.S. government agencies
Assets:
Available for sale securities	0		0		0
Fair Value, Recurring \| Level 3 \| Corporate debt securities
Assets:
Available for sale securities	$ 0		$ 0		$ 0

Financial Instruments - Amortized to fair value (Details) - USD ($) $ in Thousands	Sep. 28, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents	$ 287,431	$ 473,956
Debt Securities, Trading and Available-for-sale	214,817	249,493
Available-for-sale debt securities, amortized cost	502,081	723,580
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	185	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(18)	(132)
Total	502,248	723,449
Cash
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents	101,100	148,110
Money market funds
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents	95,079	273,546
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents	73,020	42,562
Debt Securities, Trading and Available-for-sale	149,803	186,391
Available-for-sale debt securities, amortized cost	222,712	229,040
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	124	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(13)	(87)
Total	222,823	228,953
U.S. government agencies
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents	18,232	9,738
Debt Securities, Trading and Available-for-sale	65,014	63,102
Available-for-sale debt securities, amortized cost	83,190	72,884
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	61	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	(5)	(45)
Total	$ 83,246	$ 72,840

Financial Instruments - Contractual maturity dates (Details) - USD ($) $ in Thousands	Sep. 28, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Due in one year	$ 205,923	$ 249,493
Due in one to two years	8,894	0
Total	$ 214,817	$ 249,493

Financial Instruments - Unrealized Loss Position (Details) - USD ($)	Sep. 28, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Available-for-sale securities in continuous loss position for one year or more, gross unrealized losses	$ 0	$ 0

Financial Instruments - Additional Derivative Information (Details) - USD ($) $ in Millions	Sep. 28, 2019	Dec. 31, 2018
Foreign currency exchange contract \| Not designated as hedging instrument
Derivative [Line Items]
Derivative, notional amount	$ 118.6	$ 101.4

Financial Instruments - Financial Position, Fair Value (Details) - Foreign currency exchange contract - USD ($) $ in Thousands	Sep. 28, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Fair Value Derivative Assets	$ 775	$ 623
Fair Value Derivative Liabilities	9	549
Not designated as hedging instrument \| Prepaid expenses and other current assets
Derivatives, Fair Value [Line Items]
Fair Value Derivative Assets	775	623
Fair Value Derivative Liabilities	0	0
Not designated as hedging instrument \| Accrued liabilities
Derivatives, Fair Value [Line Items]
Fair Value Derivative Assets	0	0
Fair Value Derivative Liabilities	$ 9	$ 549

Financial Instruments - Statement of Operations and Other Comprehensive Income (Details) - Foreign currency exchange contract - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Designated as hedging instrument \| Cash flow hedges
Derivative Instruments, Gain (Loss) [Line Items]
Gain recognized in OCI – effective portion	$ 0	$ 911	$ 0	$ 7,489
Designated as hedging instrument \| Reclassification out of Accumulated Other Comprehensive Income \| Unrealized Gains (Losses) on Cash Flow Hedges \| Cash flow hedges \| Revenue
Derivative Instruments, Gain (Loss) [Line Items]
Gain reclassified from OCI into income – effective portion	0	2,449	0	3,606
Not designated as hedging instrument \| Other Income, Net
Derivative Instruments, Gain (Loss) [Line Items]
Gain recognized in income	$ 2,041	$ 1,035	$ 1,567	$ 3,335

Financial Instruments - Schedule of Derivative Contracts on Consolidated Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Total amounts presented in the condensed consolidated statement of operations in which the effects of cash flow hedges are recorded in revenue	$ 347,200	$ 393,575	$ 932,646	$ 940,784
Total amounts presented in the condensed consolidated statement of operations in which the effects of cash flow hedges are recorded in operating expenses	239,248	240,061	627,027	554,132
Reclassification out of Accumulated Other Comprehensive Income \| Unrealized Gains (Losses) on Cash Flow Hedges
Derivative Instruments, Gain (Loss) [Line Items]
Gains on foreign exchange contracts designated as cash flow hedges reclassified from OCI into revenue	0	2,449	0	3,606
Cash flow hedges
Derivative Instruments, Gain (Loss) [Line Items]
Total amounts presented in the condensed consolidated statement of operations in which the effects of cash flow hedges are recorded in revenue	347,200	393,575	932,646	940,784
Total amounts presented in the condensed consolidated statement of operations in which the effects of cash flow hedges are recorded in operating expenses	$ 160,072	$ 171,328	$ 511,263	$ 586,907

Financial Instruments - Offsetting of Foreign Currency Derivative Contracts (Details) - Foreign currency exchange contract - USD ($) $ in Thousands	Sep. 28, 2019	Dec. 31, 2018
Offsetting Liabilities [Line Items]
Gross Amounts Recognized	$ 9	$ 549
Gross Amounts Offset in the Condensed Consolidated Balance Sheets	0	0
Net Amounts Presented	9	549
Gross Amounts Not Offset in Condensed Consolidated Balance Sheets, Financial Instruments	9	549
Gross Amounts Not Offset in Condensed Consolidated Balance Sheets, Cash Collateral Pledged	0	0
Net Amount	0	0
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	775	623
Gross Amounts Offset in the Condensed Consolidated Balance Sheets	0	0
Net Amounts Presented in Condensed Consolidated Balance Sheets	775	623
Gross Amounts Not Offset in Condensed Consolidated Balance Sheets, Financial Instruments	9	549
Gross Amounts Not Offset in Condensed Consolidated Balance Sheets, Cash Collateral Received	0	0
Net Amount	$ 766	$ 74

Balance Sheet Components - Deferred Revenue (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 28, 2019	Sep. 28, 2019
Deferred Revenue [Roll Forward]
Beginning balances	$ 33,361	$ 36,836
Deferral of revenue	10,515	27,325
Recognition of deferred revenue	(9,626)	29,911
Ending balances	$ 34,250	$ 34,250

Balance Sheet Components - Revenue Returns Reserves (Details) - Revenue Return Reserve - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	$ 75,044	$ 74,996	$ 104,001	$ 109,872
Increases	41,945	43,383	119,070	106,385
Returns taken	(42,845)	(39,862)	(148,927)	(137,740)
Ending balances	$ 74,144	$ 78,517	$ 74,144	$ 78,517

Balance Sheet Components - Inventories (Details) - USD ($) $ in Thousands	Sep. 28, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Components	$ 6,504	$ 8,866
Finished goods	238,592	116,005
Total inventories	$ 245,096	$ 124,871

Balance Sheet Components - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 28, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Prepaid expenses	$ 10,841	$ 18,100
Point-of-purchase (“POP”) displays, net	3,467	5,143
Prepaid marketing	2,941	3,258
Derivative asset	775	623
Other	15,352	15,201
Total prepaid expenses and other current assets	$ 33,376	$ 42,325

Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 205,163		$ 205,163		$ 192,879
Less: Accumulated depreciation and amortization	(116,931)		(116,931)		(86,593)
Property and equipment, net	88,232		88,232		106,286
Depreciation and amortization expense	13,100	$ 11,800	43,200	$ 35,400
Tooling and manufacturing equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	98,773		98,773		80,685
Furniture and office equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	20,015		20,015		22,738
Purchased and internally-developed software
Property, Plant and Equipment [Line Items]
Total property and equipment	26,634		26,634		21,741
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 59,741		$ 59,741		$ 67,715

Balance Sheet Components - Goodwill (Details) - USD ($) $ in Thousands	Sep. 28, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Goodwill	$ 60,979	$ 60,979

Balance Sheet Components - Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross	$ 41,056		$ 41,056		$ 41,056
Accumulated Amortization	(23,537)		(23,537)		(17,436)
Net	17,519		17,519		23,620
Amortization of intangible assets	2,000	$ 2,100	6,100	$ 5,866
Developed technology
Finite-Lived Intangible Assets [Line Items]
Gross	35,988		35,988		35,988
Accumulated Amortization	(21,506)		(21,506)		(15,983)
Net	14,482		14,482		20,005
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Gross	3,790		3,790		3,790
Accumulated Amortization	(857)		(857)		(451)
Net	2,933		2,933		3,339
Trademarks and other
Finite-Lived Intangible Assets [Line Items]
Gross	1,278		1,278		1,278
Accumulated Amortization	(1,174)		(1,174)		(1,002)
Net	$ 104		$ 104		$ 276

Balance Sheet Components - Estimated Future Amortization Expense (Details) - USD ($) $ in Thousands	Sep. 28, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Remaining 2019	$ 2,599
2020	6,835
2021	5,101
2022	1,552
2023	597
Thereafter	835
Net	17,519	$ 23,620
Cost of revenue
Finite-Lived Intangible Assets [Line Items]
Remaining 2019	2,392
2020	6,192
2021	4,504
2022	955
2023	0
Thereafter	0
Net	14,043
Operating expenses
Finite-Lived Intangible Assets [Line Items]
Remaining 2019	207
2020	643
2021	597
2022	597
2023	597
Thereafter	835
Net	$ 3,476

Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 28, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued sales incentives	$ 92,087	$ 126,400
Accrued revenue reserve from returns	74,144	104,001
Product warranty	44,904	45,605
Accrued manufacturing expense and freight	36,952	21,357
Accrued sales and marketing	29,725	18,171
Accrued co-op advertising and marketing development funds	27,783	30,435
Accrued research and development	16,521	8,783
Sales taxes and VAT payable	14,108	20,121
Employee-related liabilities	13,513	33,916
Inventory received but not billed	4,397	6,373
Accrued legal settlements and fees	3,375	2,821
Finance lease liabilities	464	0
Derivative liabilities	9	549
Other	7,830	18,702
Accrued liabilities	$ 365,812	$ 437,234

Balance Sheet Components - Product Warranty (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Movement in Standard and Extended Product Warranty, Increase (Decrease) [Roll Forward]
Beginning balances	$ 45,260	$ 50,468	$ 45,605	$ 87,882
Charged to cost of revenue	11,019	9,245	28,247	(1,722)
Changes related to pre-existing warranties	2,201	(1,354)	4,874	(9,226)
Settlement of claims	(13,576)	(10,504)	(33,822)	(29,079)
Ending balances	$ 44,904	$ 47,855	$ 44,904	$ 47,855

Balance Sheet Components - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 625,544	$ 678,959	$ 735,938	$ 823,963
Other comprehensive income (loss) before reclassifications			298
Other comprehensive income (loss)	(31)	(1,346)	298	3,342
Ending balance	588,974	694,721	588,974	694,721
Accumulated other comprehensive income (loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	263	4,679	(66)	(9)
Other comprehensive income (loss)	(31)	(1,346)	298	3,342
Ending balance	232	$ 3,333	232	$ 3,333
Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			66
Other comprehensive income (loss) before reclassifications			(66)
Other comprehensive income (loss)			(66)
Ending balance	0		0
Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			0
Other comprehensive income (loss) before reclassifications			0
Other comprehensive income (loss)			0
Ending balance	0		0
Unrealized Gains (Losses) on Available-for-Sale Investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(132)
Other comprehensive income (loss) before reclassifications			364
Other comprehensive income (loss)			364
Ending balance	$ 232		$ 232

Leases -Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	9 Months Ended
Leases -Narrative (Details) - USD ($) $ in Thousands	Jul. 01, 2019	Sep. 28, 2019	Sep. 29, 2018
Leases [Abstract]
Reduction of ROU Assets	$ 18,000
Lease liabilities	22,500	$ (20,975)	$ 0
Operating Lease Cost	4,300
Accelerated Depreciation of Leasehold Improvements	$ 5,200

Schedule of Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Schedule of Lease Cost (Details) - USD ($) $ in Thousands	Sep. 28, 2019	Sep. 28, 2019
Leases [Abstract]
Finance lease costs: Amortization of ROU assets	$ 989	$ 2,640
Finance lease costs: Interest on lease liabilities	0	0
Operating lease costs	5,850	16,834
Variable lease costs	1,463	4,108
Sublease income	(479)	(4,110)
Total lease costs	$ 7,823	$ 19,472

Leases Supplemental Cash Flows - Leases (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 28, 2019	Sep. 28, 2019	Sep. 29, 2018
Cash paid for amounts included in the measurement of lease liabilities:
Financing cash flows from finance leases	$ 1,302	$ 2,239	$ 0
Operating cash flows from finance leases	0	0
Operating cash flows from operating leases	6,737	20,775
ROU assets obtained in exchange for lease obligations:
Finance lease liabilities	0	0
Operating lease liabilities	$ 0	$ 288

Leases Supplemental Balance Sheet - Leases (Details) $ in Thousands	Sep. 28, 2019 USD ($)
Finance leases:
Other assets	$ 0
Accrued liabilities	464
Operating leases:
Operating lease ROU assets	71,529
Operating lease liabilities	23,313
Long-term operating lease liabilities	70,202
Total operating lease liabilities	$ 93,515

Leases Weighted Average Remaining Lease Term and Discount Rates (Details)	Sep. 28, 2019
Weighted-Average Remaining Lease Terms [Abstract]
Finance leases (in years)	9 days
Operating leases (in years)	4 years 4 months 24 days
Weighted-Average Discount Rates [Abstract]
Finance leases, percent	0.00%
Operating leases, percent	5.50%

Leases Maturity of Lease Liabilties (Details) - USD ($) $ in Thousands	Sep. 28, 2019	Dec. 31, 2018
Finance Lease, Liability, Payment, Due [Abstract]
Remaining 2019	$ 464
2020	0
2021	0
2022	0
2023	0
Thereafter	0
Total minimum lease payments	464
Less: amount representing interest	0
Total lease liabilities	464	$ 0
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Remaining 2019	8,808
2020	23,862
2021	22,459
2022	21,931
2023	20,149
Thereafter	8,321
Total minimum lease payments	105,530
Less: amount representing interest	(12,015)
Total lease liabilities	$ 93,515

Commitments and Contingencies - Narrative (Details) $ in Thousands		1 Months Ended	3 Months Ended		9 Months Ended			12 Months Ended
	Jan. 19, 2018 USD ($)	Jan. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) lawsuit	Sep. 30, 2017 USD ($)	Sep. 28, 2019 USD ($)	Sep. 29, 2018 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2017 lawsuit	Dec. 31, 2015 employee	Aug. 08, 2019	Dec. 31, 2018 USD ($)	Feb. 16, 2016 lawsuit
Loss Contingencies [Line Items]
Reduction in challenged fees, percent										90.00%
Settlement amount award to other party	$ 33,300
Bad debt expense					$ 29	$ 37
Release of product return and rebate reserves						$ 12,400
Letter of Credit
Loss Contingencies [Line Items]
Outstanding letters of credit					25,300						$ 36,600
Accrued liabilities
Loss Contingencies [Line Items]
Remaining minimum amount committed					12,900
Purchase Commitment
Loss Contingencies [Line Items]
Remaining minimum amount committed					319,000
Purchase Commitment \| Accrued liabilities
Loss Contingencies [Line Items]
Remaining minimum amount committed					19,100
Purchase Commitment to Third Party Hosting Provider
Loss Contingencies [Line Items]
Remaining minimum amount committed					$ 185,000
Aliphcom, Inc. dba Jawbone
Loss Contingencies [Line Items]
Number of defendants \| employee									6
Heart Rage Tracking
Loss Contingencies [Line Items]
Number of pending claims \| lawsuit												2
PurePulse Class Action Lawsuit
Loss Contingencies [Line Items]
Number of pending claims \| lawsuit			7					7
Number of pending claims \| lawsuit								3
Wynit Distribution \| Customer Concentration Risk
Loss Contingencies [Line Items]
Unrecognized revenue, net				$ 8,100
Accounts receivable charge recorded				35,800
Unrecoverable inventory				5,500
Accounts receivable for shipments made in the quarter				30,300			$ 30,300
Probable insurance proceeds				26,800			26,800
Insurance proceeds receivable, accounts receivable				22,700			22,700
Insurance proceeds receivable, inventory				$ 4,100			4,100
Charges offset by insurance recorded							9,000
Bad debt expense							7,600
Cost of revenue							$ 1,400
Proceeds from insurance settlement		$ 5,400	$ 21,400

Stockholders' Equity - Narrative (Details) - USD ($) shares in Thousands, $ in Millions	1 Months Ended		9 Months Ended
	Mar. 31, 2019	May 31, 2015	Sep. 28, 2019
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)			11,987
Market-based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	500
Employee Stock Options And Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to unvested options			$ 94.3
Unrecognized compensation expense related to unvested options, estimated weighted average period			1 year 10 months 24 days
Common Class A \| 2015 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Class A common stock reserved for future issuance (in shares)			26,700
Common Class A \| 2015 Employee Stock Purchase Plan \| Stock options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent of share price available to employees		85.00%

Stockholders' Equity - Stock Option Activity (Details) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended
	Sep. 28, 2019 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Balance, beginning of period (in shares) \| shares	16,263
Granted (in shares) \| shares	0
Exercised (in shares) \| shares	(817)
Canceled (in shares) \| shares	(62)
Balance, end of period (in shares) \| shares	15,384
Options exercisable (in shares) \| shares	15,384
Options vested and expected to vest (in shares) \| shares	15,158
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Balance, weighted average exercise price, beginning of period (in dollars per share)	$ 3.00
Granted, weighted average exercise price (in dollars per share)	0
Exercised, weighted average exercise price (in dollars per share)	1.53
Canceled, weighted average exercise price (in dollars per share)	5.74
Balance, weighted average exercise price, end of period (in dollars per share)	3.07
Options exercisable, weighted average exercise price (in dollars per share)	3.07
Options vested and expected to vest, weighted average exercise price (in dollars per share)	$ 3.00
Options outstanding, aggregate intrinsic value, end of period \| $	$ 21,357
Options exercisable, aggregate intrinsic value \| $	21,357
Options vested and expected to vest, aggregate intrinsic value \| $	$ 21,357
Fair value of the Class A common stock (in dollars per share)	$ 3.90

Stockholders' Equity - Restricted Stock Unit Activity (Details) - Restricted Stock Units (RSUs) shares in Thousands	9 Months Ended
	Sep. 28, 2019 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning Unvested balance (in shares) \| shares	18,376
Granted (in shares) \| shares	11,987
Vested (in shares) \| shares	(8,125)
Forfeited or canceled (in shares) \| shares	(3,959)
Ending Unvested balance (in shares) \| shares	18,279
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Beginning Unvested balance (in dollars per share) \| $ / shares	$ 6.69
Granted (in dollars per share) \| $ / shares	5.59
Vested (in dollars per share) \| $ / shares	7.33
Forfeited or canceled (in dollars per share) \| $ / shares	6.56
Ending Unvested balance (in dollars per share) \| $ / shares	$ 5.71

Stockholders' Equity - Stock Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 18,084	$ 24,115	$ 59,175	$ 73,613
Cost of revenue
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	1,446	1,999	4,397	5,129
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	10,557	14,097	34,437	43,858
Sales and marketing
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	2,587	3,638	8,900	10,996
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 3,494	$ 4,381	$ 11,441	$ 13,630

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$ 1,669	$ (18,827)	$ 3,950	$ 4,179
Effective income tax rate	(3.30%)	90.20%	(2.00%)	(2.10%)
Unrecognized tax benefits	$ 47,900		$ 47,900
Unrecognized tax benefits that would impact effective tax rate	$ 25,800		$ 25,800

Net Loss per Share - Schedule of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Numerator:
Net loss	$ (51,893)	$ (2,056)	$ (199,876)	$ (201,201)
Denominator:
Weighted-average shares of common stock—basic (in shares)	258,753	245,838	256,046	242,746
Effect of dilutive securities (in shares)	0	0	0	0
Weighted-average shares of common stock—diluted (in shares)	258,753	245,838	256,046	242,746
Net loss per share:
Basic (in dollars per share)	$ (0.20)	$ (0.01)	$ (0.78)	$ (0.83)
Diluted (in dollars per share)	$ (0.20)	$ (0.01)	$ (0.78)	$ (0.83)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(19))
-URI http://asc.fasb.org/extlink&oid=116637232&loc=SL114874131-224263

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=117326831&loc=d3e1337-109256

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- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Net Loss per Share - Antidilutive Securities (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	35,305	20,526	38,163	21,164
Stock options to purchase common stock \| Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	15,384	11,982	15,584	12,150
RSUs \| Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	18,279	8,123	20,998	8,607
Warrant \| Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	230	230	230	230
Diluted impact of ESPP \| Common Stock \| Diluted impact of ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	1,412	191	1,351	177

Significant Customer Information and Other Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018	Dec. 31, 2018
Concentration Risk [Line Items]
Revenue	$ 347,200	$ 393,575	$ 932,646	$ 940,784
Geographic Concentration Risk \| Non-US
Concentration Risk [Line Items]
Long-lived assets including property and equipment	$ 30,600		30,600		$ 36,900
Revenue \| Customer Concentration Risk \| Customer G
Concentration Risk [Line Items]
Concentration risk, percentage	12.00%	10.00%
Revenue \| Customer Concentration Risk \| Customer D
Concentration Risk [Line Items]
Concentration risk, percentage	11.00%	13.00%
Revenue \| Customer Concentration Risk \| Customer C
Concentration Risk [Line Items]
Concentration risk, percentage		12.00%		10.00%
Revenue \| Geographic Concentration Risk
Concentration Risk [Line Items]
Revenue	$ 347,200	$ 393,575	932,646	$ 940,784
Revenue \| Geographic Concentration Risk \| United States
Concentration Risk [Line Items]
Revenue	206,654	230,171	522,607	552,118
Revenue \| Geographic Concentration Risk \| Americas excluding United States
Concentration Risk [Line Items]
Revenue	16,722	24,799	51,227	56,737
Revenue \| Geographic Concentration Risk \| Europe, Middle East, and Africa
Concentration Risk [Line Items]
Revenue	82,951	104,186	257,612	234,693
Revenue \| Geographic Concentration Risk \| APAC
Concentration Risk [Line Items]
Revenue	$ 40,873	$ 34,419	$ 101,200	$ 97,236
Accounts Receivable \| Customer Concentration Risk \| Customer G
Concentration Risk [Line Items]
Concentration risk, percentage			15.00%
Accounts Receivable \| Customer Concentration Risk \| Customer D
Concentration Risk [Line Items]
Concentration risk, percentage			13.00%		10.00%
Accounts Receivable \| Customer Concentration Risk \| Customer C
Concentration Risk [Line Items]
Concentration risk, percentage			10.00%		12.00%
Accounts Receivable \| Customer Concentration Risk \| Customer B
Concentration Risk [Line Items]
Concentration risk, percentage					16.00%
Accounts Receivable \| Customer Concentration Risk \| Customer E
Concentration Risk [Line Items]
Concentration risk, percentage			11.00%
Accounts Receivable \| Customer Concentration Risk \| Customer F
Concentration Risk [Line Items]
Concentration risk, percentage			10.00%

Acquisitions - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended
Acquisitions - Narrative (Details) - USD ($) $ in Thousands	Feb. 28, 2018	Sep. 28, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill		$ 60,979	$ 60,979
Twine Health, Inc.
Business Acquisition [Line Items]
Cash paid for acquisition	$ 16,700
Goodwill	9,900
Deferred tax liabilities	1,700
Deferred tax liabilities	200
Assumed liabilities	600
Consideration held as security for indemnifications obligations	2,600
Twine Health, Inc. \| In Process Research and Development
Business Acquisition [Line Items]
Intangibles acquired	$ 5,400
Amortization period	4 years
Twine Health, Inc. \| Customer Relationships
Business Acquisition [Line Items]
Intangibles acquired	$ 3,800
Amortization period	7 years

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended
	Oct. 31, 2019	Nov. 07, 2019	Sep. 28, 2019
Subsequent Event [Line Items]
Share price			$ 3.90
Subsequent Event \| Privately Held Company
Subsequent Event [Line Items]
Total consideration	$ 6.0
Contingent consideration, earn-out	$ 2.2
Class A and Class B Common Stock \| Subsequent Event
Subsequent Event [Line Items]
Share price		$ 7.35

Label	Element	Value
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (1,127,000)
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (1,127,000)