Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 30, 2019	Mar. 31, 2018
Cash Flows from Operating Activities
Net loss	$ (79,465)	$ (80,877)
Adjustments to reconcile net loss to net cash provided by operating activities:
Provision for doubtful accounts	32	0
Provision for inventory obsolescence	1,478	6,337
Depreciation	13,373	10,456
Non-cash lease expense	7,713	0
Write-off of property and equipment	0	7,259
Amortization of intangible assets	2,060	1,748
Stock-based compensation	20,544	23,641
Deferred income taxes	(20)	(1,799)
Other	(50)	(275)
Changes in operating assets and liabilities, net of acquisition:
Accounts receivable	163,592	191,982
Inventories	(50,958)	(27,307)
Prepaid expenses and other assets	12,594	39,610
Fitbit Force recall reserve	46	(132)
Accounts payable	(81,656)	(84,155)
Accrued liabilities and other liabilities	(69,962)	(70,147)
Lease liabilities	(4,972)	0
Deferred revenue	(2,259)	(6,010)
Income taxes payable	257	(173)
Net cash provided by (used in) operating activities	(67,653)	10,158
Cash Flows from Investing Activities
Purchase of property and equipment	(6,096)	(12,616)
Purchases of marketable securities	(111,615)	(141,404)
Sales of marketable securities	0	50,795
Maturities of marketable securities	128,309	148,041
Acquisition, net of cash acquired	0	(13,646)
Net cash provided by investing activities	10,598	31,170
Cash Flows from Financing Activities
Repayment of debt	0	(747)
Payment of financing lease liability	(597)	0
Proceeds from issuance of common stock	931	992
Taxes paid related to net share settlement of restricted stock units	(6,422)	(5,179)
Net cash used in financing activities	(6,088)	(4,934)
Net increase (decrease) in cash and cash equivalents	(63,143)	36,394
Cash and cash equivalents at beginning of period	473,956	341,966
Cash and cash equivalents at end of period	$ 410,813	$ 378,360