Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net loss	$ (15,635)	$ (70,450)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	5,824	3,883
Stock-based compensation expense	21,237	7,517
Provision for doubtful accounts	755	17
Change in fair value of preferred stock warrant liability		40,333
Noncash interest expense	216	668
Loss from exit of facilities	450	232
Loss on disposals of property and equipment	8	54
Amortization of premiums on short-term investments	(164)
Changes in operating assets and liabilities:
Accounts receivable	(1,369)	(5,537)
Inventories	(36,171)	8,118
Prepaid expenses and other current assets	1,357	(2,867)
Deferred cost of revenue	1,945	(972)
Other noncurrent assets	(1,098)	(5,870)
Accounts payable and accrued liabilities	16,943	35,068
Other long-term liabilities	(541)	4,410
Deferred revenue	(3,054)	16,588
Net cash (used in) provided by operating activities	(9,297)	31,192
Cash flows from investing activities:
Purchase of property and equipment	(13,363)	(6,671)
Purchase of business, net of cash acquired		(2,959)
Purchases of short-term investments	(44,900)
Sales/maturities of short-term investments	3,000
Restricted cash		31
Net cash used in investing activities	(55,263)	(9,599)
Cash flows from financing activities:
Proceeds from borrowings, net		24,691
Repayments of borrowings		(15,000)
Holdback payment for a prior business acquisition	(500)
Proceeds from equity issued under incentive plans, net of repurchases	25,480	1,072
Net cash provided by financing activities	24,980	10,763
Net (Decrease) Increase in Cash	(39,580)	32,356
Cash and cash equivalents—Beginning of period	177,250	34,562
Cash and cash equivalents—End of period	137,670	66,918
Supplemental disclosures of cash flow information:
Cash paid for interest	455	583
Cash paid for income taxes	404	162
Supplemental disclosures of noncash investing and financing activities:
Unpaid portion of property and equipment purchases	$ 1,828	836
Unpaid initial public offering cost		2,992
Issuance of convertible preferred stock warrants in connection with debt		$ 2,032