Product Sales - Schedule of Net Product Sales (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Revenues	$ 1,927.8	$ 1,663.5	$ 1,608.0	$ 1,511.5	$ 1,582.4	$ 1,500.7	$ 1,470.1	$ 1,319.0	$ 6,710.8	$ 5,872.2	$ 4,860.4
Product
Disaggregation of Revenue [Line Items]
Revenues									4,106.2	3,718.5	3,338.4
United States | EYLEA
Disaggregation of Revenue [Line Items]
Revenues									4,076.7	3,701.9	3,323.1
United States | Libtayo
Disaggregation of Revenue [Line Items]
Revenues									14.8	0.0	0.0
United States | ARCALYST
Disaggregation of Revenue [Line Items]
Revenues									14.7	16.6	15.3
United States | Product
Disaggregation of Revenue [Line Items]
Revenues									$ 4,106.2	$ 3,718.5	$ 3,338.4