License agreements (Details 2) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		1 Months Ended	3 Months Ended								9 Months Ended	12 Months Ended
	Feb. 18, 2015	Jan. 31, 2015	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
License agreements
Long term investment			$ 35,248									$ 35,248
Total revenues			243,881	$ 187,611	$ 162,984	$ 159,275	$ 123,973	$ 198,147	$ 99,582	$ 89,792		753,751	$ 511,495	$ 354,947
Current assets			842,375				679,573					842,375	679,573
Current liabilities			$ 168,007				$ 221,061					168,007	221,061
Unrealized loss on long term investment												(4,581)
Research and development expense												$ 479,514	$ 347,523	$ 260,436
Agenus
License agreements
Fair value of common stock			$ 4.54									$ 4.54
Acquisition of outstanding voting stock of Agenus (as a percent)												9.00%
Total revenues											$ 17,200
Net loss											(72,300)
Current assets				208,900							208,900
Noncurrent assets				33,700							33,700
Current liabilities				28,300							28,300
Noncurrent liabilities				$ 137,300							$ 137,300
Unrealized loss on long term investment												$ (4,600)
Research and development expense												14,400
Agenus | Accrued and other liabilities
License agreements
Research and development expense												$ 10,100
Agenus | Development, Regulatory and Commercialization Milestones
License agreements
Reserved right to elect to co-fund of development costs (as a percent)		30.00%
Agenus | Development, Regulatory and Commercialization Milestones | Minimum
License agreements
Range of royalty payments on future global net sales (as a percent)		6.00%
Agenus | Development, Regulatory and Commercialization Milestones | Maximum
License agreements
Future contingent milestone payment		$ 155,000
Range of royalty payments on future global net sales (as a percent)		12.00%
Agenus | Development Milestones | Maximum
License agreements
Future contingent milestone payment		$ 20,000
Agenus | Stock purchase agreement
License agreements
Purchase of common stock under Stock Purchase Agreement (in shares )		7,760
Purchase price of common stock under Stock Purchase Agreement	$ 39,800	$ 35,000
Per share price of common stock under Stock Purchase Agreement	$ 5.13	$ 4.51
Minimum period for holding common stock of Agenus	12 months
Total consideration paid	$ 60,000
Long term investment	39,800
Research and development expense	$ 20,200