Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities
Net loss	$ (86,592)	$ (69,737)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation	916	702
Amortization of deferred financing costs and debt discount	230	227
Amortization and accretion of premium or discount on available-for-sale investments, net	52	403
Stock-based compensation	18,072	11,514
Unrealized foreign exchange loss	522	0
Changes in operating assets and liabilities
Prepaid, current and other assets	1,718	(916)
Accounts payable and other current liabilities	(1,981)	(3,187)
Net cash used in operating activities	(67,063)	(60,994)
Cash flows from investing activities
Purchase of available-for-sale investments	(101,217)	(19,948)
Proceeds from sales and maturities of investments	48,696	35,355
Purchase of property, plant and equipment	(7,073)	(1,392)
Net cash (used in) provided by investing activities	(59,594)	14,015
Cash flows from financing activities
Proceeds from sale of common stock, net	122,046	167,387
Proceeds related to issuance of stock for stock-based compensation arrangements, net	744	470
Net cash provided by financing activities	122,790	167,857
Net change in cash and cash equivalents	(3,867)	120,878
Beginning of period	197,945	91,060
End of period	194,078	211,938
Supplemental disclosures
Income taxes paid	0	1,790
Interest paid	1,636	1,641
Non-cash investing and financing activities
Build-to-suit lease transaction