Supplemental Statement of Cash Flows Information 2 (Details) - USD ($) $ in Millions	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Supplemental statement of cash flows information
Interest payments	$ 61	$ 60
Income taxes paid, net	130	156
Treasury common shares issued in connection with share-based incentive awards under equity compensation plans, Non-cash financing activities	47	46
Withholding taxes on share-based incentive awards, Non-cash financing activities	41	35
Treasury common shares issued in connection with discretionary stock contributions to CA, Inc. Savings Harvest Plan, Non-cash financing activities	24	23
Treasury common shares issued in connection with Employee Stock Purchase Plan, Non-cash financing activities	$ 2	$ 2