Supplemental Statement of Cash Flows Information 2 (Details) - USD ($) $ in Millions	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Supplemental Cash Flow Information [Abstract]
Interest payments	$ 60	$ 43
Income taxes paid, net	156	202
Treasury common shares issued in connection with share-based incentive awards under equity compensation plans, Non-cash financing activities	46	43
Withholding taxes on share-based incentive awards, Non-cash financing activities	35	33
Treasury common shares issued in connection with discretionary stock contributions to CA, Inc. Savings Harvest Plan, Non-cash financing activities	23	24
Treasury common shares issued in connection with Employee Stock Purchase Plan, Non-cash financing activities	$ 2	$ 2