Interim Consolidated Financial Information (Unaudited) (Details 2) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Interim Consolidated Financial Information (Unaudited)
Revenues relating to product									$ 601,015	$ 357,562	$ 235,443
Revenues relating to product royalty									74,821	48,966	28,251
Revenues relating to collaborative research and license agreement									$ 77,857	$ 104,857	$ 91,047
JAKAFI
Interim Consolidated Financial Information (Unaudited)
Revenues relating to product	$ 182,000	$ 161,300	$ 142,400	$ 115,300	$ 106,000	$ 97,800	$ 84,000	$ 69,700
JAKAVI
Interim Consolidated Financial Information (Unaudited)
Revenues relating to product royalty	23,600	18,100	17,400	15,700	14,700	12,100	12,300	9,800
Novartis and Eli Lilly
Interim Consolidated Financial Information (Unaudited)
Revenues relating to collaborative research and license agreement	$ 38,200	$ 8,200	$ 3,200	$ 28,200	$ 3,200	$ 88,200	$ 3,200	$ 10,200