Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Activities:
Net loss	$ (40,703)	$ (26,417)	$ (26,624)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	988	549	569
Amortization of premium on marketable securities	827	1,098	912
Stock-based compensation	11,730	9,200	6,146
Change in fair value of contingent consideration liability	(1,800)	230	60
Intangible impairment	1,870
Benefit from income taxes	(5,722)
Net changes in operating assets and liabilities:
Interest receivable	116	(85)	(148)
Accounts receivable	7,847	(7,213)	1,008
Prepaid expenses and other assets	376	(258)	(480)
Accounts payable and accrued liabilities	(764)	4,324	544
Accrued compensation and employee benefits	(105)	(341)	721
Deferred revenues	(8,380)	13,238	(2,190)
Net cash used in operating activities	(33,720)	(5,675)	(19,482)
Investing Activities:
Purchases of marketable securities	(257,988)	(227,802)	(118,894)
Maturities of marketable securities	337,861	127,765	51,129
Acquisition of Ceregene, Inc., net of cash received			79
Purchases of property and equipment	(2,411)	(621)	(432)
Net cash provided by / (used in) investing activities	77,462	(100,658)	(68,118)
Financing Activities:
Proceeds from public offering of common stock, net of issuance costs		93,796	69,492
Taxes paid related to net share settlement of equity awards	(1,546)	(4,556)	(2,015)
Proceeds from issuance of common stock	6,804	12,937	8,630
Claims settlement under Section 16(b)	14,452
Net cash provided by financing activities	19,710	102,177	76,107
Net increase / (decrease) in cash and cash equivalents	63,452	(4,156)	(11,493)
Cash and cash equivalents, beginning of period	6,030	10,186	21,679
Cash and cash equivalents, end of period	$ 69,482	$ 6,030	10,186
Supplemental disclosure of noncash investing activities:
Fair value of shares of common stock issued pursuant to the acquisition of Ceregene Inc.			$ 1,200