Leases - Summary of Supplemental Balance Sheet Information Related to Leases (Details) - USD ($) $ in Millions	Mar. 31, 2022	Sep. 30, 2021
Supplementary Information Balance Sheets [Abstract]
Operating lease right-of-use asset	$ 660.7	$ 676.0
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other assets	Other assets
Current operating lease liabilities	$ 181.3	$ 177.9
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other current liabilities	Other current liabilities
Operating lease liabilities	$ 520.1	$ 537.9
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other long-term liabilities	Other long-term liabilities
Total operating lease liabilities	$ 701.4	$ 715.8
Property, plant and equipment	143.4	143.2
Accumulated depreciation	(32.7)	(28.3)
Property, plant and equipment, net	110.7	114.9
Current finance lease liabilities	$ 8.2	$ 8.7
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Current portion of debt	Current portion of debt
Noncurrent finance lease liabilities	$ 250.7	$ 255.4
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Long-term debt due after one year	Long-term debt due after one year
Total finance lease liabilities	$ 258.9	$ 264.1