Goodwill (Details) - USD ($)	3 Months Ended		9 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Mar. 31, 2019
Changes in the carrying amount of goodwill by segment [Roll Forward]
Goodwill, gross			$ 10,368,000,000
Accumulated impairment losses			(2,762,000,000)
Balance as of March 31, 2019, net			7,606,000,000
Acquisitions			1,336,000,000
Foreign currency translation			1,000,000
Impairment losses	$ (53,000,000)	$ 0	(2,940,000,000)	$ 0
Goodwill, gross	11,705,000,000		11,705,000,000
Accumulated impairment losses	(5,702,000,000)		(5,702,000,000)
Balance as of December 31, 2019, net	6,003,000,000		6,003,000,000
Deferred income taxes, net	372,000,000		372,000,000		$ 355,000,000
Income tax benefit	(37,000,000)	$ (3,000,000)	(191,000,000)	$ (205,000,000)
GBS
Changes in the carrying amount of goodwill by segment [Roll Forward]
Goodwill, gross			5,300,000,000
Accumulated impairment losses			(701,000,000)
Balance as of March 31, 2019, net			4,599,000,000
Acquisitions			1,271,000,000
Foreign currency translation			1,000,000
Impairment losses			(2,675,000,000)
Goodwill, gross	6,572,000,000		6,572,000,000
Accumulated impairment losses	(3,376,000,000)		(3,376,000,000)
Balance as of December 31, 2019, net	3,196,000,000		3,196,000,000
GIS
Changes in the carrying amount of goodwill by segment [Roll Forward]
Goodwill, gross			5,068,000,000
Accumulated impairment losses			(2,061,000,000)
Balance as of March 31, 2019, net			3,007,000,000
Acquisitions			65,000,000
Foreign currency translation			0
Impairment losses			(265,000,000)
Goodwill, gross	5,133,000,000		5,133,000,000
Accumulated impairment losses	(2,326,000,000)		(2,326,000,000)
Balance as of December 31, 2019, net	2,807,000,000		2,807,000,000
Restatement Adjustment
Changes in the carrying amount of goodwill by segment [Roll Forward]
Impairment losses			(53,000,000)
Balance as of December 31, 2019, net	(53,000,000)		(53,000,000)
Deferred income taxes, net	$ 53,000,000		53,000,000
Income tax benefit			$ 53,000,000