Revenue From Contracts With Customers - Schedule of Revenues Disaggregated By Prime or Subcontractor (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 1,068	$ 706	$ 1,861	$ 1,382
Defense and Intelligence
Disaggregation of Revenue [Line Items]
Revenues	702		1,139
Civilian and Health Care
Disaggregation of Revenue [Line Items]
Revenues	366		722
Prime contractor
Disaggregation of Revenue [Line Items]
Revenues	975		1,727
Prime contractor | Defense and Intelligence
Disaggregation of Revenue [Line Items]
Revenues	660		1,077
Prime contractor | Civilian and Health Care
Disaggregation of Revenue [Line Items]
Revenues	315		650
Subcontractor
Disaggregation of Revenue [Line Items]
Revenues	93		134
Subcontractor | Defense and Intelligence
Disaggregation of Revenue [Line Items]
Revenues	42		62
Subcontractor | Civilian and Health Care
Disaggregation of Revenue [Line Items]
Revenues	$ 51		$ 72