Earnings Per Share - Schedule of Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions			1 Months Ended	2 Months Ended	3 Months Ended					9 Months Ended
		May 31, 2018	Jun. 30, 2018	May 31, 2018	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net income			$ (20)	$ 49	$ 38	$ 24	$ 104	$ 40	$ 32	$ 91	$ 176
Common share information:
Weighted average common shares outstanding for basic EPS (in shares)		165,700			164,320		142,430			165,020	142,430
Dilutive effect of stock options and equity awards (in shares)					220		0			250	0
Weighted average common shares outstanding for diluted EPS (in shares)					164,540		142,430			165,270	142,430
Earnings per share:
Basic (in dollars per share)	[1]				$ 0.23		$ 0.73			$ 0.55	$ 1.24
Diluted (in dollars per share)	[1]				$ 0.23		$ 0.73			$ 0.55	$ 1.24

[1] Earnings per share information for the three and nine months ended December 31, 2017 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.