Goodwill and Intangible Assets (Finite-Lived Intangible Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Mar. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,879.5	$ 1,879.5
Accumulated Amortization	409.9	257.9
Net Carrying Amount	1,469.6	1,621.6
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,852.0	1,852.0
Accumulated Amortization	399.2	250.8
Net Carrying Amount	1,452.8	1,601.2
Trademarks and trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	3.6	3.6
Accumulated Amortization	1.4	1.0
Net Carrying Amount	2.2	2.6
Other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	23.9	23.9
Accumulated Amortization	9.3	6.1
Net Carrying Amount	$ 14.6	$ 17.8