Acquisitions Preliminary Purchase Price Allocation (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2023	Sep. 27, 2023	Sep. 26, 2023	Dec. 31, 2022	Dec. 31, 2021
Business Acquisition [Line Items]
Goodwill	$ 6,219.2	$ 6,219.2			$ 5,749.0	$ 5,761.1
Reata Pharmaceuticals, Inc
Business Acquisition [Line Items]
Cash and cash equivalents	267.3	267.3		$ 267.3
Accounts receivable	15.9	15.9		15.9
Inventory	1,259.0	1,259.0	$ 1,300.0	1,692.0
Measurement Period Adjustments, Inventory	(433.0)	31.5
Other current assets	53.6	53.6		53.6
Operating lease assets	121.2	121.2	121.2	122.4
Measurement Period Adjustments, Operating lease assets	(1.2)
Accrued expense and other	(101.5)	(101.5)		(98.9)
Measurement Period Adjustments, Accrued expense and other	(2.6)
Debt payable	(159.9)	(159.9)		(159.9)
Contingent payable to blackstone	(300.0)	(300.0)		(300.0)
Deferred tax liability	(912.4)	(912.4)		(922.5)
Measurement Period Adjustments, Deferred tax liability	10.1
Operating lease liabilities	(151.8)	(151.8)	(151.8)	(151.8)
Other assets and liabilities, net	(2.5)	(2.5)		(2.0)
Measurement Period Adjustments, Other assets and liabilities, net	(0.5)
Total identifiable net assets	6,728.9	6,728.9		6,136.1
Measurement Period Adjustments, Total identifiable net assets	592.8
Goodwill	464.5	464.5	464.5	1,057.3
Measurement Period Adjustments, Goodwill	(592.8)
Total assets acquired and liabilities assumed	7,193.4	7,193.4		7,193.4
Reata Pharmaceuticals, Inc | Completed technology for SKYCLARYS (U.S.)
Business Acquisition [Line Items]
Intangible assets:	4,200.0	4,200.0	4,200.0	3,600.0
Measurement Period Adjustments, Intangible assets:	600.0
Reata Pharmaceuticals, Inc | In-process research and development
Business Acquisition [Line Items]
Intangible assets:	2,300.0	2,300.0	2,300.0	1,900.0
Measurement Period Adjustments, Intangible assets:	400.0
Reata Pharmaceuticals, Inc | Priority review voucher
Business Acquisition [Line Items]
Intangible assets:	100.0	100.0		100.0
Reata Pharmaceuticals, Inc | Other clinical programs
Business Acquisition [Line Items]
Intangible assets:	40.0	$ 40.0	$ 40.0	$ 20.0
Measurement Period Adjustments, Intangible assets:	$ 20.0