Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net loss	$ (44,220)	$ (15,635)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	9,170	5,824
Stock-based compensation expense	59,153	21,237
Provision for doubtful accounts	114	755
Non-cash interest expense	471	216
Loss from exit of facilities		450
Loss on disposals of property and equipment		8
Amortization of premiums on short-term investments	(280)	(164)
Changes in operating assets and liabilities:
Accounts receivable	(13,080)	(1,369)
Inventories	(37,946)	(36,171)
Prepaid expenses and other current assets	(15,270)	1,357
Operating lease right-of-use assets	13,603
Deferred cost of revenue	1,143	1,945
Other noncurrent assets	(44)	(1,098)
Accounts payable and accrued liabilities	69,448	16,943
Operating lease liabilities	856
Other long-term liabilities	(2,639)	(541)
Deferred revenue	(16,192)	(3,054)
Net cash provided by (used in) operating activities	24,287	(9,297)
Cash flows from investing activities:
Purchase of property and equipment	(38,054)	(13,363)
Purchases of short-term investments	(12,365)	(44,900)
Sales/maturities of short-term investments	53,310	3,000
Net cash provided by (used in) investing activities	2,891	(55,263)
Cash flows from financing activities:
Proceeds from equity issued under at-the-market program, net of offering costs	179,360
Proceeds from equity issued under incentive plans	24,765	25,480
Holdback payment for a prior business acquisition		(500)
Net cash provided by financing activities	204,125	24,980
Net Increase (Decrease) in cash, cash equivalents and restricted cash	231,303	(39,580)
Cash, cash equivalents and restricted cash—Beginning of period	155,564	177,250
Cash, cash equivalents and restricted cash—End of period	386,867	137,670
Cash, cash equivalents and restricted cash at end of period:
Cash and cash equivalents	385,999	137,670
Restricted cash	868
Cash, cash equivalents and restricted cash—End of period	386,867	137,670
Supplemental disclosures of cash flow information:
Cash paid for interest	2,215	455
Cash paid for income taxes	683	404
Supplemental disclosures of non-cash investing and financing activities:
Unpaid portion of property and equipment purchases	$ 8,931	$ 1,828