License Agreements (Details) (USD $)	12 Months Ended			3 Months Ended					12 Months Ended		1 Months Ended			12 Months Ended			1 Months Ended				12 Months Ended				1 Months Ended		12 Months Ended				1 Months Ended		12 Months Ended			1 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 JAKAFI (ruxolitinib)	Sep. 30, 2013 JAKAFI (ruxolitinib)	Jun. 30, 2013 JAKAFI (ruxolitinib)	Mar. 31, 2013 JAKAFI (ruxolitinib)	Dec. 31, 2012 JAKAFI (ruxolitinib)	Dec. 31, 2013 JAKAFI (ruxolitinib)	Dec. 31, 2012 JAKAFI (ruxolitinib)	Jan. 31, 2010 Collaboration and License Agreement with Novartis	Dec. 31, 2009 Collaboration and License Agreement with Novartis	Nov. 30, 2009 Collaboration and License Agreement with Novartis deliverable	Dec. 31, 2013 Collaboration and License Agreement with Novartis	Dec. 31, 2012 Collaboration and License Agreement with Novartis	Dec. 31, 2011 Collaboration and License Agreement with Novartis	Nov. 30, 2009 Collaboration and License Agreement with Novartis Pre-specified events Maximum	Nov. 30, 2009 Collaboration and License Agreement with Novartis Development milestones Maximum	Nov. 30, 2009 Collaboration and License Agreement with Novartis Regulatory milestones Maximum	Nov. 30, 2009 Collaboration and License Agreement with Novartis Commercialized milestones Maximum	Dec. 31, 2013 Collaboration and License Agreement with Novartis LY3009104(INCB28060) Development milestones	Dec. 31, 2011 Collaboration and License Agreement with Novartis LY3009104(INCB28060) Development milestones	Dec. 31, 2011 Collaboration and License Agreement with Novartis LY3009104(INCB28060) Regulatory milestones	Dec. 31, 2012 Collaboration and License Agreement with Novartis JAKAFI (ruxolitinib) Regulatory milestones	Jul. 31, 2010 License, Development and Commercialization Agreement with Lilly	Dec. 31, 2009 License, Development and Commercialization Agreement with Lilly deliverable	Dec. 31, 2013 License, Development and Commercialization Agreement with Lilly	Dec. 31, 2012 License, Development and Commercialization Agreement with Lilly	Dec. 31, 2011 License, Development and Commercialization Agreement with Lilly	Dec. 31, 2010 License, Development and Commercialization Agreement with Lilly Maximum	Dec. 31, 2009 License, Development and Commercialization Agreement with Lilly Pre-specified events Maximum	Dec. 31, 2009 License, Development and Commercialization Agreement with Lilly Development milestones Maximum	Dec. 31, 2012 License, Development and Commercialization Agreement with Lilly Development milestones Phase III	Dec. 31, 2010 License, Development and Commercialization Agreement with Lilly Development milestones Phase IIa	Dec. 31, 2010 License, Development and Commercialization Agreement with Lilly Development milestones Phase IIb	Dec. 31, 2009 License, Development and Commercialization Agreement with Lilly Regulatory milestones Maximum	Dec. 31, 2009 License, Development and Commercialization Agreement with Lilly Commercialized milestones Maximum	Jan. 31, 2006 Collaborative Research and License Agreement with Pfizer
License agreements
Upfront and immediate milestone payment to be received under license agreement													$ 210,000,000				$ 1,100,000,000	$ 162,000,000	$ 450,000,000	$ 500,000,000											$ 665,000,000	$ 150,000,000				$ 365,000,000	$ 150,000,000
Amount recognized and received for the achievement of a predefined milestone																					25,000,000	15,000,000	10,000,000	40,000,000									50,000,000	30,000,000	19,000,000
Royalty payment obligations	8,300,000	3,300,000												0
Number of deliverables under license agreement													2													2
Upfront payment received under license agreement												150,000,000														90,000,000												40,000,000
Immediate milestone payment received under license agreement											60,000,000
Reimbursable costs recorded as deferred revenue												10,900,000
Reimbursable costs included in accounts receivable														1,700,000	2,100,000												0	0
Research and development expenses reimbursed														5,100,000	4,400,000	3,600,000											0	100,000	200,000
Contract revenues	91,047,000	156,948,000	91,948,000											78,200,000	94,100,000	79,100,000											12,900,000	62,900,000	12,900,000
Additional milestone payment received under license agreement														25,000,000	40,000,000	25,000,000												50,000,000
Range of royalty payments on future global net sales, upper range (as a percent)																														20.00%
Associated future global development costs from the initiation of a Phase IIb trial, if elected to co-develop, percentage																									30.00%	30.00%
Product royalty revenues	$ 28,251,000	$ 3,652,000		$ 8,400,000	$ 8,200,000	$ 5,800,000	$ 5,900,000	$ 3,700,000	$ 28,300,000	$ 3,700,000
Period of notice for termination of license agreement																																						90 days