Supplementary Data - Selected Quarterly Financial Data (Unaudited) (Details) - USD ($)	2 Months Ended	3 Months Ended								5 Months Ended	10 Months Ended	12 Months Ended
	May 31, 2018	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, 2019	Mar. 31, 2020		Mar. 31, 2019		Mar. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Revenue		$ 1,099,000,000	$ 1,126,000,000	$ 1,172,000,000	$ 1,107,000,000	$ 1,094,000,000	$ 1,075,000,000	$ 1,068,000,000	$ 793,000,000			$ 4,504,000,000		$ 4,030,000,000		$ 2,819,000,000
Costs of services		853,000,000	863,000,000	908,000,000	836,000,000	817,000,000	816,000,000	813,000,000	597,000,000			3,460,000,000		3,043,000,000		2,155,000,000
Selling, general and administrative		73,000,000	77,000,000	81,000,000	72,000,000	74,000,000	76,000,000	89,000,000	61,000,000			303,000,000		300,000,000		182,000,000
Depreciation and amortization		91,000,000	92,000,000	90,000,000	101,000,000	116,000,000	76,000,000	74,000,000	64,000,000			374,000,000		330,000,000		167,000,000
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, transaction 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
Other (income) expense, net		99,000,000	(35,000,000)	(2,000,000)	0	34,000,000	2,000,000	(4,000,000)	(24,000,000)			62,000,000		8,000,000		0
Total costs and expenses		1,983,000,000	1,051,000,000	1,135,000,000	1,065,000,000	1,107,000,000	1,027,000,000	1,032,000,000	752,000,000			5,234,000,000		3,918,000,000		2,620,000,000
(Loss) 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
Income tax expense		(95,000,000)	22,000,000	8,000,000	11,000,000	6,000,000	10,000,000	12,000,000	12,000,000			(54,000,000)		40,000,000		(9,000,000)
Net (loss) income	$ 49,000,000	$ (789,000,000)	$ 53,000,000	$ 29,000,000	$ 31,000,000	$ (19,000,000)	$ 38,000,000	$ 24,000,000	$ 29,000,000		$ 23,000,000	$ (676,000,000)		$ 72,000,000		$ 208,000,000
Basic (in dollars per share)		$ (4.89)	$ 0.33	$ 0.18	$ 0.19	$ (0.12)	$ 0.23	$ 0.15	$ 0.18			$ (4.17)	[1]	$ 0.44	[1]	$ 1.46	[1]
Diluted (in dollars per share)		(4.89)	0.33	0.18	0.19	(0.12)	0.23	0.14	0.17			$ (4.17)	[1]	$ 0.44	[1]	$ 1.46	[1]
Cash dividends per common share (in dollars per share)		$ 0.06	$ 0.06	$ 0.06	$ 0.06	$ 0.05	$ 0.05	$ 0.05	$ 0.05

[1] (1) Earnings per common share information for the fiscal year ended March 31, 2018 is computed using the 142.43 million shares of Perspecta common stock resulting from the Distribution as Perspecta did not operate as a stand-alone entity during the period, and therefore, no Perspecta common stock, stock options or other equity awards were outstanding and no dividends were declared or paid by Perspecta.