Revenues (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues
Total revenues	$ 382.3
Before topic 606
Revenues
Total revenues		$ 384.1
Product revenues, net
Revenues
Total revenues	334.5
Product revenues, net | Before topic 606
Revenues
Total revenues		264.8
JAKAFI
Revenues
Total revenues	313.7
JAKAFI | Before topic 606
Revenues
Total revenues		251.1
ICLUSIG
Revenues
Total revenues	20.8
ICLUSIG | Before topic 606
Revenues
Total revenues		13.7
Product royalty revenues
Revenues
Total revenues	47.7
Product royalty revenues | Before topic 606
Revenues
Total revenues		29.2
Milestone revenues | Before topic 606
Revenues
Total revenues		90.0
Other revenues
Revenues
Total revenues	$ 0.1
Other revenues | Before topic 606
Revenues
Total revenues		$ 0.1