Product Sales - Schedule of Net Product Sales (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 2,422.9	$ 2,294.0	$ 1,952.0	$ 1,828.2	$ 1,863.5	$ 1,743.7	$ 1,577.8	$ 1,372.6	$ 8,497.1	$ 6,557.6	$ 5,145.6
Product
Disaggregation of Revenue [Line Items]
Revenues									5,567.6	4,834.4	4,106.2
United States | EYLEA
Disaggregation of Revenue [Line Items]
Revenues									4,947.2	4,644.2	4,076.7
United States | Libtayo
Disaggregation of Revenue [Line Items]
Revenues									270.7	175.7	14.8
United States | Praluent
Disaggregation of Revenue [Line Items]
Revenues									150.9
United States | REGEN-COV
Disaggregation of Revenue [Line Items]
Revenues									185.7	0.0	0.0
United States | ARCALYST
Disaggregation of Revenue [Line Items]
Revenues									13.1	14.5	14.7
United States | Product
Disaggregation of Revenue [Line Items]
Revenues									$ 5,567.6	$ 4,834.4	$ 4,106.2