Property and Equipment (Summary) (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, net	$ 91.1	$ 140.9
Depreciation expense	44.0	45.6	$ 50.8
Distribution Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	15.2	29.7
Building
Property, Plant and Equipment [Line Items]
Property and equipment, gross	0.0	50.4
Less accumulated depreciation and amortization		(4.9)
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	42.9	43.4
Property and Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	16.7	25.9
Computer Equipment and Software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	197.0	162.4
Depreciable Assets
Property, Plant and Equipment [Line Items]
Property and equipment, gross	271.8	311.8
Less accumulated depreciation and amortization	(181.9)	(172.1)
Property and equipment, net	89.9	139.7
Land
Property, Plant and Equipment [Line Items]
Property and equipment, net	$ 1.2	1.2
Distribution Equipment Held Under Finance Lease
Property, Plant and Equipment [Line Items]
Property and equipment, gross		9.5
Less accumulated depreciation and amortization		$ (7.7)