Strategic Alliances (Details) - USD ($)	1 Months Ended				2 Months Ended	3 Months Ended			6 Months Ended		67 Months Ended
	May 31, 2016	Sep. 30, 2015	Jan. 31, 2015	Dec. 31, 2010	Jun. 30, 2016	Jun. 30, 2016	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Dec. 31, 2015	Jul. 31, 2015	Mar. 31, 2013
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue from transfer of intellectual property and other						$ 68,281,000	$ 17,673,000		$ 86,898,000	$ 30,202,000
Deferred revenue					$ 198,500,000	198,500,000			198,500,000		$ 198,500,000	$ 232,900,000
Payment of grant repayment obligation								$ 25,900,000
Grant repayment						0	0		0	25,889,000
VFMCRP
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone revenue recognized					0
VFMCRP | Development and License Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License revenue, initial payment	$ 50,000,000					50,000,000			50,000,000
Royalty revenue, obligation period after first product sale	10 years
VFMCRP | Regulatory Milestones
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Additional milestone payment to be received	$ 37,000,000
VFMCRP | Launch and Sales-based Milestones
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Additional milestone payment to be received	195,000,000
VFMCRP | Exclusive Option
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Additional milestone payment to be received	$ 555,000,000
Pfizer | Collaborative Arrangement, Product
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Non-refundable and non-creditable upfront payment			$ 295,000,000.0
Additional milestone payment to be received			275,000,000
Revenue from transfer of intellectual property and other						17,700,000	$ 17,700,000		35,300,000	30,200,000
Deferred revenue					194,200,000	194,200,000			194,200,000		194,200,000
Tesaro
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone revenue recognized									0	$ 0
Additional milestone payment to be received				$ 30,000,000
Upfront payment under license agreements				6,000,000.0
Milestone payment received											20,000,000
Additional milestone payment				$ 85,000,000
Period from first commercial sale				12 years
Merck | Collaborative Arrangement, Product
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Non-refundable and non-creditable upfront payment		$ 23,000,000
Additional milestone payment to be received		5,000,000
Milestone payment received									18,600,000
Amount payable each year		$ 5,000,000
Period for yearly payment		4 years
Intangible assets, estimated useful lives		13 years
Accrued Expenses | Pfizer | Collaborative Arrangement, Product
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue					70,600,000	70,600,000			70,600,000		70,600,000
Accrued Expenses | Merck | Collaborative Arrangement, Product
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payment received									4,900,000
Other Noncurrent Liabilities | Pfizer | Collaborative Arrangement, Product
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue					$ 123,600,000	$ 123,600,000			123,600,000		$ 123,600,000
Other Noncurrent Liabilities | Merck | Collaborative Arrangement, Product
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payment received									$ 13,700,000
Minimum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible assets, estimated useful lives									3 years
Minimum | Pfizer | Collaborative Arrangement, Product
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Each milestone payment			20,000,000
Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Intangible assets, estimated useful lives									20 years
Maximum | Pfizer | Collaborative Arrangement, Product
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Each milestone payment			$ 90,000,000
Pharmsynthez
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Ownership percentage					17.00%	17.00%			17.00%		17.00%
Rxi Pharmaceuticals Corporation
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments														$ 50,000,000.0
Pharmsynthez Note Receivable | Notes | Pharmsynthez
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Debt face amount													$ 3,000,000.0