Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating activities
Net loss	$ (91,641)	$ (66,364)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	2,388	2,266
Amortization of intangible assets	1,263	1,249
Stock-based compensation expense	10,535	9,002
Amortization of debt issuance costs	350	349
Accretion of debt discount	4,907	4,650
Finance lease amortization expense	270	360
Noncash operating lease expense	5,208	1,536
Changes in operating assets and liabilities:
Accounts receivable	(1,066)	2,078
Inventory	(2,754)	(2,332)
Prepaid expenses and other current assets	2,056	4,341
Other assets	(19,731)	(1,568)
Accounts payable	(20,273)	4,169
Accrued expenses and other	(4,686)	(7,480)
Accrued compensation	(15,107)	(10,191)
Net cash used in operating activities	(128,281)	(57,935)
Investing activities
Purchase of fixed assets	(1,181)	(2,679)
Net cash used in investing activities	(1,181)	(2,679)
Financing activities
Proceeds from exercise of stock options, ESPP, and RSU vesting	6,961	2,426
Payments of finance lease principal	(258)	(292)
Net cash provided by financing activities	6,703	2,134
Effect of exchange rates on cash and cash equivalents	(246)	(7)
Net decrease in cash and cash equivalents	(123,005)	(58,487)
Cash and cash equivalents at beginning of period	532,756	487,429
Cash and cash equivalents at end of period	409,751	428,942
Supplemental disclosures of cash flow information:
Cash paid for interest	4,271	4,381
Cash paid for income taxes	$ 672	$ 414