Revenue From Contracts With Customers - Schedule of Revenues Disaggregated By Contract Type (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 1,075	$ 722	$ 2,936	$ 2,104
Cost-reimbursable
Disaggregation of Revenue [Line Items]
Revenues	265		646
Fixed-price
Disaggregation of Revenue [Line Items]
Revenues	602		1,684
Time-and-materials
Disaggregation of Revenue [Line Items]
Revenues	208		606
Defense and Intelligence
Disaggregation of Revenue [Line Items]
Revenues	709		1,848
Defense and Intelligence | Cost-reimbursable
Disaggregation of Revenue [Line Items]
Revenues	240		580
Defense and Intelligence | Fixed-price
Disaggregation of Revenue [Line Items]
Revenues	373		985
Defense and Intelligence | Time-and-materials
Disaggregation of Revenue [Line Items]
Revenues	96		283
Civilian and Health Care
Disaggregation of Revenue [Line Items]
Revenues	366		1,088
Civilian and Health Care | Cost-reimbursable
Disaggregation of Revenue [Line Items]
Revenues	25		66
Civilian and Health Care | Fixed-price
Disaggregation of Revenue [Line Items]
Revenues	229		699
Civilian and Health Care | Time-and-materials
Disaggregation of Revenue [Line Items]
Revenues	$ 112		$ 323