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