Goodwill (Details) $ in Millions	3 Months Ended
	Jun. 30, 2020 USD ($)
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
Acquisitions	16
Foreign currency translation	24
Goodwill, gross	11,613
Accumulated impairment losses	(9,556)
Balance as of June 30, 2020, net	2,057
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
Acquisitions	16
Foreign currency translation	24
Goodwill, gross	6,547
Accumulated impairment losses	(4,490)
Balance as of June 30, 2020, net	2,057
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
Acquisitions	0
Foreign currency translation	0
Goodwill, gross	5,066
Accumulated impairment losses	(5,066)
Balance as of June 30, 2020, net	$ 0