Divestitures - Income Statement (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense			$ 0	$ 18
Total income from discontinued operations	$ 0	$ 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, 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