Revenues - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($) wholesaler	Mar. 31, 2022 USD ($)
Disaggregation of Revenue [Line Items]
Number of wholesalers | wholesaler	2
Product revenues	$ 2,463.0	$ 2,531.8
Distributor One
Disaggregation of Revenue [Line Items]
Percentage of revenues from major distributors	27.30%	26.30%
Distributor Two
Disaggregation of Revenue [Line Items]
Percentage of revenues from major distributors	7.40%	10.50%
Contract manufacturing, royalty and other revenue
Disaggregation of Revenue [Line Items]
Product revenues	$ 319.1	$ 66.1
LEQEMBI Collaboration
Disaggregation of Revenue [Line Items]
Product revenues	$ (18.9)	$ 0.0