Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities
Net loss	$ (69,737)	$ (53,986)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation	702	102
Amortization of deferred financing costs and debt discount	227	232
Amortization and accretion of premium or discount on available-for-sale investments, net	403	439
Stock-based compensation	11,514	9,533
Changes in operating assets and liabilities
Prepaid, current and other assets	(916)	(238)
Accounts payable and other current liabilities	(3,187)	2,407
Interest payable	0	0
Net cash used in operating activities	(60,994)	(41,511)
Cash flows from investing activities
Purchase of available-for-sale investments	(19,948)	(26,560)
Maturity of available-for-sale investments	35,355	40,813
Sale of available-for-sale investments	0	1,999
Purchase of furniture, fixtures and equipment	(1,392)	(1,855)
Net cash provided by investing activities	14,015	14,397
Cash flows from financing activities
Proceeds from sale of common stock, net of commissions and underwriting discounts	168,479	47,100
Payments of stock issuance costs and expenses	(1,092)	0
Proceeds from exercise of stock options	313	1,269
Proceeds from exercise of warrants	0	9
Proceeds from exercise of stock purchase rights	297	96
Tax withholdings related to restricted stock awards	(140)	0
Net cash provided by financing activities	167,857	48,474
Net change in cash and cash equivalents	120,878	21,360
Beginning of period	91,060	85,586
End of period	211,938	106,946
Supplemental disclosures
Income taxes paid	1,790	600
Interest paid	$ 1,641	$ 1,635