Strategic Alliances (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended			6 Months Ended
	Jan. 31, 2015	Dec. 31, 2010	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	Mar. 31, 2013
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue			$ 272,400			$ 272,400		$ 6,700
Grant repayment			0	$ 25,900	$ 0	25,889	$ 0
Pfizer | Collaborative Arrangement, Product
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Non-refundable upfront payment	$ 295,000
Additional milestone payment to be received	275,000
Revenue from sale of intellectual property						30,200
Deferred revenue			264,800			264,800
Tesaro
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Additional milestone payment to be received		$ 30,000
Upfront payment under license agreements		6,000
Milestone payment received						5,000
Additional milestone payment		$ 85,000				25,000
Period from first commercial sale		12 years
Accrued Expenses | Pfizer | Collaborative Arrangement, Product
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue			70,600			70,600
Other Noncurrent Liabilities | Pfizer | Collaborative Arrangement, Product
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue			$ 194,200			$ 194,200
Minimum | Pfizer | Collaborative Arrangement, Product
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payment ranges	20,000
Maximum | Pfizer | Collaborative Arrangement, Product
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payment ranges	$ 90,000
Rxi Pharmaceuticals Corporation
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments									$ 50,000