Property and Equipment - Summary of Property and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Property, Plant and Equipment, Net, by Type [Abstract]
Total cost	$ 1,910.6	$ 1,716.0
Less: accumulated depreciation and amortization	(1,096.8)	(1,032.3)
Property and Equipment, Net	$ 813.8	683.7
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	$ 877.4	789.2
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	$ 576.2	522.4
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	$ 374.0	324.3
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	$ 83.0	$ 80.1