Collaborative and Other Relationships - Summary of Activity Related to Sage Therapeutics (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2024
Collaborative arrangements and non-collaborative arrangement transactions
Share of net profit from sage therapeutics, Percent	50.00%		50.00%
Collaboration profit sharing/(loss reimbursement)	$ 69.3	$ 50.5	$ 197.3	$ 164.5
Sage Therapeutics
Collaborative arrangements and non-collaborative arrangement transactions
Collaboration profit sharing/(loss reimbursement)	9.0	5.9	20.5	5.9
Sage Therapeutics | Forecast
Collaborative arrangements and non-collaborative arrangement transactions
Potential future milestone payments commitment to third party					$ 75.0
Research and development | Sage Therapeutics
Collaborative arrangements and non-collaborative arrangement transactions
Expense incurred by the collaboration	8.4	72.0	29.6	158.9
Expense reflected within statements of income	4.2	36.0	14.8	79.5
Selling, general and administrative | Sage Therapeutics
Collaborative arrangements and non-collaborative arrangement transactions
Expense incurred by the collaboration	28.4	54.0	82.9	152.3
Expense reflected within statements of income	$ 14.2	$ 27.0	$ 41.5	$ 76.1