Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net loss	$ (9,732)	$ (6,634)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,849	1,656
Stock-based compensation expense	17,864	4,429
Provision for doubtful accounts	181	201
Non-cash interest expense	344
Loss from exit of facilities		129
Amortization of premiums on short-term investments	(182)
Changes in operating assets and liabilities:
Accounts receivable	8,702	26,986
Inventories	2,187	(5,430)
Prepaid expenses and other current assets	(8,116)	(11,643)
Operating lease right-of-use assets	3,440
Deferred cost of revenue	552	2,090
Other noncurrent assets	685	(353)
Accounts payable and accrued liabilities	(18,606)	(18,474)
Operating lease liabilities	(2,491)
Other long-term liabilities	(581)	(118)
Deferred revenue	(7,800)	(7,476)
Net cash used in operating activities	(10,704)	(14,637)
Cash flows from investing activities:
Purchase of property and equipment	(5,071)	(3,407)
Purchases of short-term investments	(12,365)
Sales/maturities of short-term investments	27,310
Net cash provided by (used in) investing activities	9,874	(3,407)
Cash flows from financing activities:
Proceeds from equity issued under incentive plans	10,091	1,544
Proceeds from equity issued under at-the-market program, net of offering costs	98,025
Net cash provided by financing activities	108,116	1,544
Net Increase (Decrease) in cash, cash equivalents and restricted cash	107,286	(16,500)
Cash, cash equivalents and restricted cash—Beginning of period	155,564	177,250
Cash, cash equivalents and restricted cash—End of period	262,850	160,750
Cash, cash equivalents and restricted cash at end of period:
Cash and cash equivalents	236,500	160,750
Restricted cash	26,350
Cash, cash equivalents and restricted cash—End of period	262,850	160,750
Supplemental disclosures of cash flow information:
Cash paid for interest	542
Cash paid for income taxes	557	180
Supplemental disclosures of non-cash investing and financing activities:
Unpaid portion of property and equipment purchases	4,769	$ 1,460
Unpaid portion of at-the-market offering costs	$ 249