Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating activities
Net loss	$ (87,074)	$ (64,683)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	13,077	12,706
Depreciation and amortization	4,301	3,625
Payment of accrued interest on long-term debt	(2,593)	0
Loss on extinguishment of long-term debt	7,143	0
Amortization of debt discount and deferred financing costs	6,141	575
Loss on equity securities	300	0
Amortization of discount on short-term investments	(150)	(11)
Non-cash operating lease expense	2,417	2,069
Conversion of accrued interest to long-term debt	0	1,565
Provision for inventory obsolescence and bad debts	15	722
Changes in operating assets and liabilities:
Accounts receivable	1,390	(2,224)
Inventory	(6,792)	(7,161)
Prepaid expenses and other assets	4,663	(5,292)
Accounts payable	(4,286)	(2,027)
Accrued liabilities	(1,533)	1,133
Accrued compensation and other employee benefits	(2,366)	(1,232)
Customer deposits	(4,912)	(1,705)
Deferred revenue	1,739	(6,244)
Operating lease liabilities	(2,262)	(1,701)
Net cash used in operating activities	(70,782)	(69,885)
Investing activities
Purchases of property and equipment	(6,808)	(1,832)
Proceeds from sale of short-term investments	17,218	2,500
Proceeds from maturity of short-term investments	89,784	84,070
Purchases of short-term investments	(38,804)	(122,084)
Net cash provided by (used in) investing activities	61,390	(37,346)
Financing activities
Proceeds from issuance of 2025 convertible senior notes and borrowings under long-term debt agreement	230,000	20,000
Fees paid for issuance of 2025 convertible senior notes and long-term debt borrowings	(7,403)	(100)
Repayment of long-term debt	(80,000)	0
Fees paid upon extinguishment of debt	(4,845)	0
Proceeds from sale of common stock, net	0	68,273
Proceeds from issuance of common stock warrants	737	1,821
Tax withholdings related to net share settlements of restricted stock units	(2,012)	(1,474)
Proceeds from issuance of common stock for employee stock purchase plan	2,190	1,952
Proceeds from exercise of stock options	13,077	15,899
Net cash provided by financing activities	151,744	106,371
Net increase (decrease) in cash and cash equivalents	142,352	(860)
Effect of exchange rate changes on cash and cash equivalents	67	(54)
Cash and cash equivalents
Beginning of period	29,033	24,356
End of period	171,452	23,442
Right-of-use assets obtained in exchange for lease obligations	$ 524	$ 27,364