Revenue - Schedule of Revenues Disaggregated By Customer Type (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 1,172	$ 1,068	$ 2,279	$ 1,861
U.S. federal government, including independent agencies
Disaggregation of Revenue [Line Items]
Revenues	1,095	998	2,135	1,727
Non-federal (state, local and other)
Disaggregation of Revenue [Line Items]
Revenues	77	70	144	134
Defense and Intelligence
Disaggregation of Revenue [Line Items]
Revenues	777	702	1,529	1,139
Defense and Intelligence | U.S. federal government, including independent agencies
Disaggregation of Revenue [Line Items]
Revenues	773	700	1,521	1,136
Defense and Intelligence | Non-federal (state, local and other)
Disaggregation of Revenue [Line Items]
Revenues	4	2	8	3
Civilian and Health Care
Disaggregation of Revenue [Line Items]
Revenues	395	366	750	722
Civilian and Health Care | U.S. federal government, including independent agencies
Disaggregation of Revenue [Line Items]
Revenues	322	298	614	591
Civilian and Health Care | Non-federal (state, local and other)
Disaggregation of Revenue [Line Items]
Revenues	$ 73	$ 68	$ 136	$ 131