Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2020
Operating activities
Net loss	$ (66,507)	$ (95,009)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3,952	4,036
Premium amortization and discount accretion on investment securities	151	1,887
Stock-based compensation	9,855	19,374
Non-cash lease expense	3,849	3,880
Amortization of debt discount and issuance cost	215	2,180
Other non-cash charges	415
Other non-cash (benefits)		(341)
Loss on debt extinguishment		5,848
Provision for credit losses		1,445
Changes in operating assets and liabilities
Accounts receivable	(829)	(5,972)
Inventory	(1,815)	(5,410)
Prepaid expenses and other current assets	(4,464)	(5,610)
Other assets	(9,499)	99
Accounts payable	(6,378)	(4,684)
Accrued compensation	(2,519)	495
Other accrued liabilities	2,331	6,602
Deferred revenue	35,492	(4,900)
Net cash used in operating activities	(35,751)	(76,080)
Investing activities
Purchases of investments	(162,176)	(266,139)
Proceeds from sale of investments		11,500
Proceeds from maturity of investments	62,780	142,815
Purchases of property and equipment, net	(1,599)	(10,130)
Net cash used in investing activities	(100,995)	(121,954)
Financing activities
Proceeds from exercise of stock options	5,983	10,808
Proceeds from issuance of common stock under employee stock purchase plan	2,147	3,062
Proceeds from Convertible Notes		278,317
Loan payment		(78,757)
Proceeds from public offering	107,595
Net cash provided by financing activities	115,725	213,430
Net (decrease) increase in cash, cash equivalents and restricted cash	(21,021)	15,396
Cash, cash equivalents and restricted cash, beginning of period		61,981
Cash, cash equivalents and restricted cash, end of period	29,983	77,377
Supplemental disclosure of cash flow information:
Cash paid for interest	7,343	2,976
Supplemental non-cash investing and financing activities:
Obtaining right-of-use assets in exchange for lease liabilities	28,191
Purchases of property and equipment in accounts payable and accruals	$ 323	$ 255