Revenue - Narrative (Details) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2020 USD ($) payment	Dec. 31, 2024 USD ($) wholesaler	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Jul. 31, 2023
Disaggregation of Revenue [Line Items]
Number of wholesalers | wholesaler		2
Percentage of total revenues		18.10%	17.20%	16.70%
Revenue		$ 9,675.9	$ 9,835.6	$ 10,173.4
Contract manufacturing revenue
Disaggregation of Revenue [Line Items]
Revenue		$ 592.1	848.2	417.7
Remaining performance obligation, amount	$ 500.0
Remaining performance obligation, number of payments | payment	3
LEQEMBI Collaboration
Disaggregation of Revenue [Line Items]
Share of non-controling interest recognized		50.00%			50.00%
Alzheimer's collaboration revenue
Disaggregation of Revenue [Line Items]
Revenue		$ 59.9	$ 0.0	$ 0.0
Distributor One
Disaggregation of Revenue [Line Items]
Percentage receivables of wholesale distributor accounted in consolidated receivables		27.20%	24.60%
Distributor Two
Disaggregation of Revenue [Line Items]
Percentage receivables of wholesale distributor accounted in consolidated receivables		11.70%	11.60%
Distributor One
Disaggregation of Revenue [Line Items]
Percentage of revenue from major distributors		25.90%	27.00%	26.80%
Distributor Two
Disaggregation of Revenue [Line Items]
Percentage of revenue from major distributors		13.40%	9.90%	11.10%