Revenues - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024 USD ($) wholesaler	Sep. 30, 2023 USD ($) wholesaler	Sep. 30, 2024 USD ($) wholesaler	Sep. 30, 2023 USD ($) wholesaler
Disaggregation of Revenue [Line Items]
Number of wholesalers | wholesaler	2	2	2	2
Product revenues	$ 2,465.8	$ 2,530.3	$ 7,221.2	$ 7,449.3
Distributor One
Disaggregation of Revenue [Line Items]
Percentage of revenues from major distributors	25.90%	26.90%	25.60%	27.10%
Distributor Two
Disaggregation of Revenue [Line Items]
Percentage of revenues from major distributors	14.80%	10.50%	12.90%	9.10%
Contract manufacturing, royalty and other revenue
Disaggregation of Revenue [Line Items]
Product revenues	$ 250.2	$ 304.2	$ 555.6	$ 781.2
LEQEMBI Collaboration
Disaggregation of Revenue [Line Items]
Share of non-controling interest recognized	50.00%		50.00%