Revenues - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2024 USD ($) wholesaler	Mar. 31, 2023 USD ($) wholesaler
Disaggregation of Revenue [Line Items]
Number of wholesalers | wholesaler	2	2
Product revenues	$ 2,290.5	$ 2,463.0
Distributor One
Disaggregation of Revenue [Line Items]
Percentage of revenues from major distributors	25.60%	27.30%
Distributor Two
Disaggregation of Revenue [Line Items]
Percentage of revenues from major distributors	11.70%	7.40%
Contract manufacturing, royalty and other revenue
Disaggregation of Revenue [Line Items]
Product revenues	$ 184.6	$ 300.2
LEQEMBI Collaboration
Disaggregation of Revenue [Line Items]
Share of non-controling interest recognized	50.00%