Property and Equipment - Summary of Property and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Property, Plant and Equipment, Net, by Type [Abstract]
Total cost	$ 1,950.7	$ 1,910.6
Less: accumulated depreciation and amortization	(1,180.7)	(1,096.8)
Property and Equipment, Net	$ 770.0	813.8
Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	35 years
Buildings and leasehold improvements [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total cost	$ 868.2	877.4
Buildings and leasehold improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Buildings and leasehold improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	35 years
Software [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total cost	$ 609.4	576.2
Software [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Software [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Equipment and Furniture [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total cost	$ 390.6	374.0
Equipment and Furniture [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Equipment and Furniture [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Land [Member]
Property, Plant and Equipment, Net, by Type [Abstract]
Total cost	$ 82.5	$ 83.0