Goodwill, Capitalized Software and Other Intangible Assets 3 (Details) $ in Millions	9 Months Ended
	Dec. 31, 2017 USD ($)
Goodwill activity by segment
Balance at March 31, 2017	$ 6,857
Acquisitions	(99)	[1]
Foreign currency translation adjustment	41
Balance at December 31, 2017	6,799
Mainframe Solutions
Goodwill activity by segment
Balance at March 31, 2017	4,178
Acquisitions	0
Foreign currency translation adjustment	0
Balance at December 31, 2017	4,178
Enterprise Solutions
Goodwill activity by segment
Balance at March 31, 2017	2,598
Acquisitions	(99)	[1]
Foreign currency translation adjustment	41
Balance at December 31, 2017	2,540
Services
Goodwill activity by segment
Balance at March 31, 2017	81
Acquisitions	0
Foreign currency translation adjustment	0
Balance at December 31, 2017	$ 81

[1] Acquisitions amount relates to purchase price allocation adjustments that occurred during the nine months ended December 31, 2017.