Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 267,761	$ 225,853
Short-term investments	59,432
Receivable from collaboration partner	227,310	391,558
Prepaid expenses and other current assets	49,653	15,877
Restricted cash	1,449	930
Total current assets	605,605	634,218
Property and equipment, net	60,994	58,142
Long-term investments	21,515
Intangible assets	648,799	644,299
Deferred income tax assets	284,933	57,011
Restricted cash, net of current	11,687	12,206
Goodwill	18,643	18,643
Other non-current assets	7,331	7,072
Total assets	1,659,507	1,431,591
Current liabilities:
Accounts payable, accrued expenses and other current liabilities	135,026	186,203
Contingent consideration	4,951	4,900
Current portion of build-to-suit lease obligation	127
Total current liabilities	140,104	266,103
Contingent consideration	952,604	262,368
Build-to-suit lease obligation, excluding current portion	17,244	17,406
Other non-current liabilities	15,881	13,035
Total liabilities	1,125,833	558,912
Commitments and contingencies (Note 11)
Stockholders' equity:
Preferred stock, $0.01 par value per share; 1,000,000 shares authorized; no shares issued and outstanding
Common stock, $0.01 par value per share; 340,000,000 shares authorized; 165,555,633 and 163,905,342 shares issued and outstanding at June 30, 2016 and December 31, 2015, respectively	1,656	1,639
Additional paid-in capital	745,475	684,841
Accumulated other comprehensive loss	(550)
Retained earnings (accumulated deficit)	(212,907)	186,199
Total stockholders' equity	533,674	872,679
Total liabilities and stockholders' equity	$ 1,659,507	1,431,591
Revolving Credit Facility [Member]
Current liabilities:
Borrowings under Credit Facility		$ 75,000