Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 317,361	$ 225,853
Receivable from collaboration partner	186,593	391,558
Prepaid expenses and other current assets	24,416	15,877
Restricted cash	1,140	930
Total current assets	529,510	634,218
Property and equipment, net	59,849	58,142
Intangible assets	644,299	644,299
Deferred income tax assets	53,148	57,011
Restricted cash, net of current	11,996	12,206
Goodwill	18,643	18,643
Other non-current assets	8,037	7,072
Total assets	1,325,482	1,431,591
Current liabilities:
Accounts payable, accrued expenses and other current liabilities	121,995	186,203
Contingent consideration	4,924	4,900
Current portion of build-to-suit lease obligation	110
Total current liabilities	127,029	266,103
Contingent consideration	268,303	262,368
Build-to-suit lease obligation, excluding current portion	17,278	17,406
Other non-current liabilities	12,658	13,035
Total liabilities	$ 425,268	$ 558,912
Commitments and contingencies (Note 13)
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; 164,581,922 and 163,905,342 shares issued and outstanding at March 31, 2016 and December 31, 2015, respectively	$ 1,646	$ 1,639
Additional paid-in capital	707,870	684,841
Accumulated other comprehensive loss	(317)
Retained earnings	191,015	186,199
Total stockholders’ equity	900,214	872,679
Total liabilities and stockholders’ equity	$ 1,325,482	1,431,591
Revolving Credit Facility [Member]
Current liabilities:
Borrowings under Credit Facility		$ 75,000