Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating activities:
Net loss	$ (164,997,000)	$ (146,829,000)
Adjustments to reconcile net loss to net cash used for operating activities:
Stock-based compensation expense	34,183,000	40,312,000
Depreciation and amortization	2,135,000	1,480,000
Amortization of debt discount	1,013,000	780,000
Realized gain on available-for-sale securities	0	(8,000)
Amortization of premium (accretion of discount) on short-term investments	39,000	(3,264,000)
Impairment of property and equipment	61,000	80,000
Loss on disposal of property and equipment		53,000
Change in operating assets and liabilities:
Accounts receivable	6,225,000	(2,303,000)
Inventory	(17,781,000)	14,860,000
Prepaid expenses and other assets	6,799,000	(5,549,000)
Accounts payable	9,309,000	(15,236,000)
Accrued clinical and manufacturing liabilities	6,104,000	1,603,000
Accrued payroll and employee liabilities	(2,013,000)	(3,263,000)
Other accrued liabilities	(13,343,000)	19,681,000
Net cash used for operating activities	(132,266,000)	(97,603,000)
Investing activities:
Purchases of short-term investments	(92,040,000)	(287,579,000)
Maturities and sales of short-term investments	248,525,000	395,406,000
Purchases of property and equipment	(4,319,000)	(3,251,000)
Net cash provided by investing activities	152,166,000	104,576,000
Financing activities:
Net proceeds from sale of common stock		(110,000)
Proceeds from stock option exercises	1,833,000	20,239,000
Proceeds from purchases under the Employee Stock Purchase Plan	1,507,000	1,170,000
Proceeds from warrant exercises	3,000
Net cash provided by financing activities	3,343,000	21,299,000
Net increase in cash and cash equivalents	23,243,000	28,272,000
Cash and cash equivalents at beginning of year	71,898,000	31,836,000
Cash and cash equivalents at end of period	$ 95,141,000	$ 60,108,000