Divestitures - Income Statement (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total income from discontinued operations	$ 0	$ 0	$ 35
USPS Separation | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue			431
Costs of services			311
Selling, general and administrative			50
Depreciation and amortization			33
Restructuring costs			1
Interest expense			8
Other (income) expense, net			(25)
Total costs and expenses			378
Total income from discontinued operations, before income taxes			53
Income tax expense			18
Total income from discontinued operations			$ 35