Acquisitions - Pro Forma Information (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions		2 Months Ended	3 Months Ended								10 Months Ended	12 Months Ended
	May 31, 2018	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, 2019	Mar. 31, 2020		Mar. 31, 2019		Mar. 31, 2018
Business Acquisition, Pro Forma Information [Abstract]
Revenue			$ 1,099	$ 1,126	$ 1,172	$ 1,107	$ 1,094	$ 1,075	$ 1,068	$ 793		$ 4,504		$ 4,030		$ 2,819
Net income (loss)		$ 49	$ (789)	$ 53	$ 29	$ 31	$ (19)	$ 38	$ 24	$ 29	$ 23	$ (676)		$ 72		$ 208
Earnings per common share
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]
Number of shares from distribution in a spinoff (in shares)	165,700											161,990		164,560		142,430
Weighted average common shares outstanding for diluted EPS (in shares)												161,990		164,820		142,430
Vencore and KeyPoint
Business Acquisition, Pro Forma Information [Abstract]
Revenue		244														$ 1,384
Net income (loss)		$ (57)														33
Vencore and KeyPoint
Business Acquisition, Pro Forma Information [Abstract]
Revenue											1,270
Net income (loss)											$ 185
Vencore and KeyPoint | Pro Forma Combined for the Spin-Off and Mergers
Business Acquisition, Pro Forma Information [Abstract]
Revenue														$ 4,274		4,203
Net income (loss)														$ 28		$ 128
Earnings per common share
Basic (in dollars per share)														$ 0.17		$ 0.77
Diluted (in dollars per share)														$ 0.17		$ 0.77
Vencore and KeyPoint | Effects of the Spin-Off
Business Acquisition, Pro Forma Information [Abstract]
Revenue														$ 0		$ 0
Net income (loss)														(7)		(1)
Vencore and KeyPoint | Effects of the Mergers
Business Acquisition, Pro Forma Information [Abstract]
Revenue														0		0
Net income (loss)														$ 20		$ (112)

[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.