Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Operating activities
Net loss	$ (149,377)	$ (109,063)
Adjustments to reconcile net loss to net cash used in operating activities:
Acquired in-process research and development	8,000	1,000
Depreciation and amortization expense	1,479	227
Stock-based compensation expense	21,146	9,381
Non-cash interest expense	5,082	4,544
Changes in operating assets and liabilities:
Accounts receivable	169
Inventories	(7,275)
Other assets	(2,296)	(1,136)
Accounts payable	5,859	2,303
Accrued expenses	6,421	7,806
Deferred revenues	912
Other liabilities	(49)	33
Net cash used in operating activities	(109,929)	(84,905)
Investing activities
Acquisition of product candidate and technology licenses and milestone payments	(8,000)
Purchase of property and equipment	(590)	(943)
Net cash used in investing activities	(8,590)	(943)
Financing activities
Proceeds from sale of common stock, net of issuance costs	204,969	179,763
Proceeds from exercise of stock options	2,568	3,345
Proceeds from issuance of common stock under Employee Stock Purchase Plan	1,040	248
Net cash provided by financing activities	208,577	183,356
Increase in cash and cash equivalents	90,058	97,508
Cash and cash equivalents at beginning of period	230,146	256,861
Cash and cash equivalents at end of period	320,204	354,369
Non-cash investing and financing activities
Purchase of property and equipment - cash not paid as of period end	139	456
Acquired in-process research and development - milestone not paid as of period end		1,000
Stock option exercise proceeds receivable as of period end	2,875
Supplemental cash flow information
Cash paid for interest	$ 3,019	$ 3,052