Segment Information - Schedule of Operating Results By Segment (Details) $ in Millions	3 Months Ended	9 Months Ended
Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) segment	Dec. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments \| segment			2
Revenue	$ 1,075	$ 722	$ 2,936	$ 2,104
Acquired
Segment Reporting Information [Line Items]
Depreciation and amortization	37	17	98	52
Defense and Intelligence
Segment Reporting Information [Line Items]
Revenue	709		1,848
Civilian and Health Care
Segment Reporting Information [Line Items]
Revenue	366		1,088
Operating segments
Segment Reporting Information [Line Items]
Revenue	1,075	722	2,936	2,104
Segment profit	111	79	275	228
Depreciation and amortization	76	46	214	116
Operating segments \| Defense and Intelligence
Segment Reporting Information [Line Items]
Revenue	709	374	1,848	1,051
Segment profit	85	31	181	81
Depreciation and amortization	34	21	98	54
Operating segments \| Civilian and Health Care
Segment Reporting Information [Line Items]
Revenue	366	348	1,088	1,053
Segment profit	26	48	94	147
Depreciation and amortization	$ 42	$ 25	$ 116	$ 62

The current period expense charged against earnings on long-lived, physical assets not used in production, and which are not intended for resale, to allocate or recognize the cost of such assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset; or to reflect consumption during the period of an asset that is not used in production.

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