Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Operating Activities:
Net loss	$ (17,445)	$ (14,553)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	428	250
Amortization of premium on marketable securities	464	583
Stock-based compensation	5,836	4,036
Change in fair value of contingent consideration liability	(1,800)	80
Intangible impairment	1,870
Benefit from income taxes	(748)
Net changes in operating assets and liabilities:
Interest receivable	30	27
Accounts receivable	5,189	(3,814)
Prepaid expenses and other assets	(131)	(1,076)
Accounts payable and accrued liabilities	449	1,329
Accrued compensation and employee benefits	(833)	(1,221)
Deferred revenues	(3,727)	17,164
Net cash provided by / (used in) operating activities	(10,418)	2,805
Investing Activities:
Purchases of marketable securities	(120,895)	(67,003)
Maturities of marketable securities	133,235	50,604
Purchases of property and equipment	(2,082)	(465)
Net cash provided by / (used in) investing activities	10,258	(16,864)
Financing Activities:
Proceeds from public offering of common stock, net of issuance costs		93,796
Taxes paid related to net share settlement of equity awards	(48)
Proceeds from issuance of common stock	4,946	9,347
Net cash provided by financing activities	4,898	103,143
Net increase in cash and cash equivalents	4,738	89,084
Cash and cash equivalents, beginning of period	6,030	10,186
Cash and cash equivalents, end of period	10,768	$ 99,270
Supplemental disclosure of noncash investing activities:
Property and equipment included in accrued liabilities	$ 84