Revenue from Contracts with Customers 1 (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of revenue
Total revenue		$ 895	$ 1,034	$ 1,833	$ 2,059
Mainframe Solutions
Disaggregation of revenue
Total revenue		388		828
Enterprise Solutions
Disaggregation of revenue
Total revenue		436		866
Services
Disaggregation of revenue
Total revenue		71		139
Point-in-Time, Including Professional Services
Disaggregation of revenue
Total revenue		297		634
Over Time
Disaggregation of revenue
Total revenue		598		1,199
Perpetual Licenses
Disaggregation of revenue
Total revenue		70		146
On-Premise Term Licenses
Disaggregation of revenue
Total revenue		157		350
Maintenance
Disaggregation of revenue
Total revenue		473		960
SaaS
Disaggregation of revenue
Total revenue		124		238
Professional Services
Disaggregation of revenue
Total revenue		71	$ 75	139	$ 150
United States
Disaggregation of revenue
Total revenue		592		1,164
EMEA
Disaggregation of revenue
Total revenue	[1]	186		415
Other
Disaggregation of revenue
Total revenue		$ 117		$ 254

[1] Consists of Europe, the Middle East and Africa.