Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating activities:
Net loss	$ (113,234,000)	$ (90,935,000)
Adjustments to reconcile net loss to net cash used for operating activities:
Stock-based compensation expense	30,608,000	15,522,000
Depreciation and amortization	959,000	711,000
Amortization of debt discount	507,000	428,000
Realized gain on short-term investments	(8,000)	0
Accretion of discount on short-term investments	(2,437,000)	(864,000)
Impairment on property and equipment	54,000
Loss on disposal of property and equipment	53,000	3,000
Change in operating assets and liabilities:
Accounts receivable	(2,169,000)	(4,012,000)
Prepaid expenses and other assets	2,454,000	(3,039,000)
Inventory	9,762,000	(17,287,000)
Accounts payable	(8,866,000)	(13,790,000)
Accrued clinical and manufacturing liabilities	913,000	(8,934,000)
Accrued payroll and employee liabilities	(4,415,000)	(1,974,000)
Other accrued liabilities	13,687,000	1,729,000
Net cash used for operating activities	(72,132,000)	(122,442,000)
Investing activities:
Purchases of short-term investments	(204,358,000)	(157,885,000)
Maturities and sales of short-term investments	284,606,000	22,500,000
Purchases of property and equipment	(4,299,000)	(2,238,000)
Net cash provided by (used for) investing activities	75,949,000	(137,623,000)
Financing activities:
Net proceeds from sale of common stock		363,127,000
Proceeds from stock option exercises	16,215,000	10,641,000
Proceeds from purchases under the Employee Stock Purchase Plan	1,170,000	648,000
Net cash provided by financing activities	17,385,000	374,416,000
Net increase in cash and cash equivalents	21,202,000	114,351,000
Cash and cash equivalents at beginning of year	31,836,000	144,583,000
Cash and cash equivalents at end of period	$ 53,038,000	258,934,000
Supplemental disclosure of cash flow information:
Interest paid		1,000,000
Cumulative effect of adoption of new accounting standard		$ 1,574,000