Revenue From Contracts With Customers - Schedule of Revenues Disaggregated By Contract Type (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
Cost-reimbursable
Disaggregation of Revenue [Line Items]
Revenues	251		381
Fixed-price
Disaggregation of Revenue [Line Items]
Revenues	607		1,082
Time-and-materials
Disaggregation of Revenue [Line Items]
Revenues	210		398
Defense and Intelligence
Disaggregation of Revenue [Line Items]
Revenues	702		1,139
Defense and Intelligence | Cost-reimbursable
Disaggregation of Revenue [Line Items]
Revenues	231		340
Defense and Intelligence | Fixed-price
Disaggregation of Revenue [Line Items]
Revenues	367		612
Defense and Intelligence | Time-and-materials
Disaggregation of Revenue [Line Items]
Revenues	104		187
Civilian and Health Care
Disaggregation of Revenue [Line Items]
Revenues	366		722
Civilian and Health Care | Cost-reimbursable
Disaggregation of Revenue [Line Items]
Revenues	20		41
Civilian and Health Care | Fixed-price
Disaggregation of Revenue [Line Items]
Revenues	240		470
Civilian and Health Care | Time-and-materials
Disaggregation of Revenue [Line Items]
Revenues	$ 106		$ 211