Accounting for Share-Based Compensation 1 (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Recognized share-based compensation
Share-based compensation expense before tax	$ 29	$ 25	$ 61	$ 54
Income tax benefit	(9)	(8)	(20)	(18)
Net share-based compensation expense	20	17	41	36
Costs of Licensing and Maintenance
Recognized share-based compensation
Share-based compensation expense before tax	2	1	4	3
Cost of Professional Services
Recognized share-based compensation
Share-based compensation expense before tax	0	1	1	2
Selling and Marketing
Recognized share-based compensation
Share-based compensation expense before tax	10	9	20	19
General and Administrative
Recognized share-based compensation
Share-based compensation expense before tax	11	8	23	19
Product Development and Enhancements
Recognized share-based compensation
Share-based compensation expense before tax	$ 6	$ 6	$ 13	$ 11