Collaborative and Other Relationships - Summary of Activity Related to Sage Therapeutics (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 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)	$ 62.4	$ 56.9	$ 128.0	$ 114.0
Sage Therapeutics
Collaborative arrangements and non-collaborative arrangement transactions
Collaboration profit sharing/(loss reimbursement)	6.5		11.5
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	9.6	52.1	21.2	86.9
Expense reflected within statements of income	4.8	26.1	10.6	43.5
Selling, general and administrative | Sage Therapeutics
Collaborative arrangements and non-collaborative arrangement transactions
Expense incurred by the collaboration	26.9	60.1	54.5	98.3
Expense reflected within statements of income	$ 13.5	$ 30.0	$ 27.3	$ 49.1