Goodwill (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Changes in the carrying amount of goodwill by segment [Roll Forward]
Goodwill, gross			$ 11,573
Accumulated impairment losses			(9,556)
Balance as of March 31, 2020, net			2,017
Acquisition related adjustments			18
Divestitures			(1,355)
Assets held for sale			(4)
Foreign currency translation			60
Goodwill, gross	$ 10,292		10,292
Accumulated impairment losses	(9,556)		(9,556)
Balance as of December 31, 2020, net	736		736
Goodwill impairment losses	0	$ 53	0	$ 2,940
GBS
Changes in the carrying amount of goodwill by segment [Roll Forward]
Goodwill, gross			6,507
Accumulated impairment losses			(4,490)
Balance as of March 31, 2020, net			2,017
Acquisition related adjustments			18
Divestitures			(1,355)
Assets held for sale			(4)
Foreign currency translation			60
Goodwill, gross	5,226		5,226
Accumulated impairment losses	(4,490)		(4,490)
Balance as of December 31, 2020, net	736		736
GIS
Changes in the carrying amount of goodwill by segment [Roll Forward]
Goodwill, gross			5,066
Accumulated impairment losses			(5,066)
Balance as of March 31, 2020, net			0
Acquisition related adjustments			0
Divestitures			0
Assets held for sale			0
Foreign currency translation			0
Goodwill, gross	5,066		5,066
Accumulated impairment losses	(5,066)		(5,066)
Balance as of December 31, 2020, net	$ 0		$ 0