Divestitures - Income Statement (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2019	Jun. 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	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