Share-Based Payments - Share-Based Compensation Expense by Share-Based Compensation Program (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Jul. 02, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense		$ (75.0)	$ (64.8)	$ (224.0)	$ (217.8)
Subtotal		131.1	452.0	275.4	609.7
Capitalized share-based compensation costs		(2.4)	(2.6)	(8.0)	(8.5)
Share-based compensation expense included in total costs and expenses		128.7	449.4	267.4	601.2
Reata Pharmaceuticals, Inc
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense		0.0	387.0	0.0	387.0
Human Immunology Biosciences
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense	$ 56.4	56.4	0.0	56.4	0.0
Market stock units
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense		0.2	0.7	0.6	4.2
Time-vested restricted stock units
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense		59.1	53.4	174.7	175.0
Performance stock units settled in stock
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense		13.0	7.8	35.2	27.1
Performance stock units settled in cash
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense		(0.5)	0.1	(2.5)	4.8
Employee stock purchase plan
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense		1.9	2.0	8.2	8.8
Options
Summary of share based compensation expense associated with different programs [Abstract]
Share-based compensation expense		$ 1.0	$ 1.0	$ 2.8	$ 2.8