Segment Information 1 (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2018		Jun. 30, 2017
Summary of segment revenue and reconciliation to total consolidated revenue
Segment revenue	$ 1,052		$ 1,025
Impact of segment policies that differ from U.S. GAAP	(114)	[1]	0
Total consolidated revenue	938		1,025
Mainframe Solutions
Summary of segment revenue and reconciliation to total consolidated revenue
Segment revenue	553		536
Total consolidated revenue	440
Enterprise Solutions
Summary of segment revenue and reconciliation to total consolidated revenue
Segment revenue	425		414
Total consolidated revenue	430
Services
Summary of segment revenue and reconciliation to total consolidated revenue
Segment revenue	74		$ 75
Total consolidated revenue	$ 68

[1] The manner in which the Company measures and recognizes revenues for segment reporting was not revised upon adoption of Topic 606. For segment reporting purposes, the Company follows its previous Topic 605 policies, which recognizes software license revenue ratably, except for sales of perpetual licenses on a stand-alone basis, which are recognized at a point-in-time.