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Other Consolidated Financial Statement - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025
Collaborative arrangements and non-collaborative arrangement transactions
Net unrealized (gains) losses recognized on equity securities	$ (42.8)	$ (5.3)	$ (61.9)	$ 35.7
Prepaid Taxes	648.9		648.9		$ 693.6
Other liabilities, noncurrent	820.9		820.9		748.5
Accrued income taxes	177.5		177.5		$ 166.4
Sage and Denali
Collaborative arrangements and non-collaborative arrangement transactions
Net unrealized (gains) losses recognized on equity securities		$ 10.1
Denali Therapeutics
Collaborative arrangements and non-collaborative arrangement transactions
Net unrealized (gains) losses recognized on equity securities	$ 46.7		$ 65.9	45.7
Sage Therapeutics
Collaborative arrangements and non-collaborative arrangement transactions
Net unrealized (gains) losses recognized on equity securities				$ 23.0