Stockholders' Equity - Capital Stock and Share Repurchases (Details) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2017 USD ($) $ / shares shares	Jun. 30, 2017 USD ($) $ / shares shares	Sep. 30, 2017 USD ($) vote $ / shares shares	Apr. 03, 2017 shares	Mar. 31, 2017 $ / shares shares	[1]
Equity [Abstract]
Common stock, authorized (in shares)	750,000,000		750,000,000		750,000,000
Common stock, par value (in dollars per share) | $ / shares	$ 0.01		$ 0.01		$ 0.01
Preferred stock, authorized (in shares)	1,000,000		1,000,000		1,000,000
Preferred stock, par value (in dollars per share) | $ / shares	$ 0.01		$ 0.01		$ 0.01
Number of votes per common share | vote			1
Share Repurchases [Abstract]
Initial authorization (in shares)				2,000,000,000.0
Number of Shares Repurchased (in shares)	591,505	250,000	841,505
Average Price per Share (in dollars per share) | $ / shares	$ 78.20	$ 77.39	$ 77.96
Amount (in millions) | $	$ 47	$ 19	$ 66

[1] Certain prior year amounts were adjusted to retroactively reflect the legal capital of DXC.