Acquisitions (Pro Forma Information) (Details) - Achillion - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Business Acquisition [Line Items]
Pro forma revenue	$ 1,444.6	$ 1,203.3	$ 2,889.4	$ 2,343.7
Pro forma net (loss) income	$ (1,068.1)	$ 440.3	$ (493.2)	$ 956.0