Goodwill, Capitalized Software and Other Intangible Assets 3 (Details) $ in Millions	6 Months Ended
	Sep. 30, 2016 USD ($)
Goodwill activity by segment
Balance at March 31, 2016	$ 6,086
Foreign currency translation adjustment	(3)
Balance at September 30, 2016	6,083
Mainframe Solutions
Goodwill activity by segment
Balance at March 31, 2016	4,178
Foreign currency translation adjustment	0
Balance at September 30, 2016	4,178
Enterprise Solutions
Goodwill activity by segment
Balance at March 31, 2016	1,827
Foreign currency translation adjustment	(3)
Balance at September 30, 2016	1,824
Services
Goodwill activity by segment
Balance at March 31, 2016	81
Foreign currency translation adjustment	0
Balance at September 30, 2016	$ 81