Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (18,000)	$ (22,645)	$ (116,445)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	597	180	23
Amortization of investments	1,602
Stock-based compensation	45,813	30,917	18,806
Amortization of debt discount and debt issuance costs	635	1,644	2,183
Amortization of intangible asset	1,441	679	646
Changes in assets and liabilities:
Accounts receivable, net	(38,144)	(49,907)	(21,205)
Inventory	(112,095)	(18,967)	(27,542)
Prepaid and other current assets	(17,636)	(10,366)	510
Other long-term assets	642	(900)
Interest receivable	(1,329)
Accrued interest payable	(428)	(210)	(310)
Deferred revenue	(2,214)	136	1,656
Accounts payable, accrued expenses and other current liabilities	114,741	65,913	37,602
Other long-term liabilities	2,629	(5,840)	9,373
Net cash used in operating activities	(21,746)	(9,366)	(94,703)
CASH FLOWS FROM INVESTING ACTIVITIES:
Sale and maturities of securities	301,989
Purchases of securities	(678,700)
Purchases of furniture, fixtures and equipment	(252)	(2,478)	(58)
Net cash used in investing activities	(376,963)	(2,478)	(58)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock, net of transaction costs		440,108	264,840
Proceeds from issuance of common stock under employee stock purchase plan	1,957	2,165	1,043
Proceeds from exercise of stock options, net of transaction costs	5,158	24,478	26,402
Payment of transaction costs for conversion of preferred stock	(504)		(39)
Payment on debt from royalty-bearing instrument	(50,336)	(31,652)	(14,690)
Transaction costs related to exchange of exchangeable senior notes			(121)
Taxes related to stock-based awards	(15,182)	(25,487)	(6,184)
Net cash (used in) provided by financing activities	(58,907)	409,612	271,251
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS AND RESTRICTED CASH	(457,616)	397,768	176,490
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH, BEGINNING OF PERIOD	648,495	250,727	74,237
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH, END OF PERIOD	190,879	648,495	250,727
Cash paid during the year for:
Interest	2,043	4,591	21,527
Income taxes	207	67	850
Supplemental disclosure of non-cash transactions:
Laxdale milestone		8,457
Initial recognition of operating lease right-of-use asset		$ 8,995
Exchange of exchangeable senior notes into common stock			29,490
Conversion of Series A Convertible Preferred Stock into common stock	$ 18,020		$ 2,514