Divestitures - Income Statement (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total income from discontinued operations	$ 0	$ 73	$ 35	$ 198
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		726	431	2,113
Costs of services		544	311	1,589
Selling, general and administrative		37	50	94
Depreciation and amortization		41	33	115
Restructuring costs		3	1	10
Interest expense		4	8	11
Other income, net		0	(25)	0
Total costs and expenses		629	378	1,819
Total income from discontinued operations, before income taxes		97	53	294
Income tax expense	$ 0	24	18	96
Total income from discontinued operations		$ 73	$ 35	$ 198