Segment Information - Reconciliation of Reportable Segment Profit to the Statements of Operations (Details) - USD ($)	3 Months Ended								5 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2017	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Not allocated to segments:
Stock-based compensation										$ (23,000,000)	$ (11,000,000)	$ (6,000,000)
Impairment charges	$ (796,000,000)	$ 0	$ 0	$ 0						(796,000,000)	0	0
Restructuring costs	(13,000,000)	0	(2,000,000)	(2,000,000)	$ (7,000,000)	$ (1,000,000)	$ (2,000,000)	$ 0	$ (14,000,000)	(17,000,000)	(10,000,000)	(14,000,000)
Separation and integration-related costs	(26,000,000)	(20,000,000)	(20,000,000)	(19,000,000)	(22,000,000)	(19,000,000)	(21,000,000)	(44,000,000)		(85,000,000)	(106,000,000)	(90,000,000)
Interest expense, net	(32,000,000)	(34,000,000)	(36,000,000)	(35,000,000)	(37,000,000)	(37,000,000)	(37,000,000)	(10,000,000)		(137,000,000)	(121,000,000)	(12,000,000)
Income before taxes	$ (884,000,000)	$ 75,000,000	$ 37,000,000	$ 42,000,000	$ (13,000,000)	$ 48,000,000	$ 36,000,000	$ 41,000,000		(730,000,000)	112,000,000	199,000,000
Operating segments
Segment Reporting Information [Line Items]
Total segment profit										596,000,000	527,000,000	390,000,000
Not allocated to segments:
Amortization of acquired intangible assets										(374,000,000)	(330,000,000)	(167,000,000)
Corporate
Not allocated to segments:
Stock-based compensation										(23,000,000)	(11,000,000)	(6,000,000)
Impairment charges										(796,000,000)	0	0
Restructuring costs										(17,000,000)	(4,000,000)	(14,000,000)
Separation and integration-related costs										(85,000,000)	(106,000,000)	(90,000,000)
Interest expense, net										(137,000,000)	(121,000,000)	(12,000,000)
Other unallocated, net										(62,000,000)	(8,000,000)	0
Series of Individually Immaterial Business Acquisitions | Operating segments
Not allocated to segments:
Amortization of acquired intangible assets										(206,000,000)	(165,000,000)	(69,000,000)
Defense and Intelligence | Operating segments
Segment Reporting Information [Line Items]
Total segment profit										444,000,000	331,000,000	168,000,000
Not allocated to segments:
Amortization of acquired intangible assets										(66,000,000)	(74,000,000)	(34,000,000)
Civilian and Health Care | Operating segments
Segment Reporting Information [Line Items]
Total segment profit										152,000,000	196,000,000	222,000,000
Not allocated to segments:
Amortization of acquired intangible assets										$ (102,000,000)	$ (91,000,000)	$ (64,000,000)