Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating activities
Net loss	$ (85,993)	$ (87,074)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	23,689	13,077
Depreciation and amortization	4,347	4,301
Payment of accrued interest on long-term debt	0	(2,593)
Loss on equity securities	0	300
Loss on extinguishment of long-term debt	0	7,143
Amortization of debt discount and deferred financing costs	1,069	6,141
Accretion of discount on short-term investments	(2,436)	(150)
Non-cash operating lease expense	2,553	2,417
Provision for inventory obsolescence and bad debts	2,258	15
Changes in operating assets and liabilities:
Accounts receivable	(4,739)	1,390
Inventory	(10,348)	(6,792)
Prepaid expenses and other assets	(8,265)	4,663
Accounts payable	6,975	(4,286)
Accrued liabilities	(1,161)	(1,533)
Accrued compensation and other employee benefits	958	(2,366)
Customer deposits	(304)	(4,912)
Deferred revenue	1,540	1,739
Operating lease liabilities	(3,173)	(2,262)
Net cash used in operating activities	(73,030)	(70,782)
Investing activities
Purchases of property and equipment	(4,704)	(6,808)
Purchase of internal-use software assets	(651)	0
Proceeds from sale of short-term investments	4,000	17,218
Proceeds from maturity of short-term investments	24,764	89,784
Purchases of short-term investments	(260,239)	(38,804)
Net cash (used in) provided by investing activities	(236,830)	61,390
Financing activities
Proceeds from issuance of 2025 convertible senior notes and borrowings under long-term debt agreement	0	230,000
Fees paid for issuance of 2025 convertible senior notes and long-term debt borrowings	0	(7,403)
Repayment of long-term debt	0	(80,000)
Fees paid upon extinguishment of debt	0	(4,845)
Proceeds from issuance of common stock warrants	0	737
Tax withholdings related to net share settlements of restricted stock units	(2,585)	(2,012)
Proceeds from issuance of common stock for employee stock purchase plan	2,427	2,190
Proceeds from exercise of stock options	5,547	13,077
Repayment of finance lease obligations	(170)	0
Net cash provided by financing activities	5,219	151,744
Net increase (decrease) in cash and cash equivalents	(304,641)	142,352
Effect of exchange rate changes on cash and cash equivalents	(40)	67
Cash and cash equivalents
Beginning of period	411,848	29,033
End of period	107,167	171,452
Supplemental Cash Flow Information [Abstract]
Finance lease right-of-use assets obtained in exchange for lease obligations	$ 448	$ 524