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Segment Information - Schedule of Operating Results By Segment (Details) $ in Millions	3 Months Ended		4 Months Ended	6 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2018 USD ($) segment	Sep. 30, 2017 USD ($)
Segment Reporting [Abstract]
Number of reportable segments \| segment				2
Segment Reporting Information [Line Items]
Revenue	$ 1,068	$ 706		$ 1,861	$ 1,382
Defense and Intelligence
Segment Reporting Information [Line Items]
Revenue	702			1,139
Civilian and Health Care
Segment Reporting Information [Line Items]
Revenue	366			722
Operating segments
Segment Reporting Information [Line Items]
Revenue	1,068	706		1,861	1,382
Segment profit	92	80		164	149
Depreciation and amortization	74	33		138	70
Operating segments \| Defense and Intelligence
Segment Reporting Information [Line Items]
Revenue	702	357		1,139	677
Segment profit	71	27		96	50
Depreciation and amortization	34	15		64	33
Operating segments \| Civilian and Health Care
Segment Reporting Information [Line Items]
Revenue	366	349		722	705
Segment profit	21	53		68	99
Depreciation and amortization	40	18		74	37
Vencore and KeyPoint
Segment Reporting Information [Line Items]
Revenue			$ 490
Depreciation and amortization	$ 36	$ 18		$ 61	$ 35