Segment Information (Details)	3 Months Ended		9 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			2
Revenues	$ 5,021,000,000	$ 5,178,000,000	$ 14,762,000,000	$ 15,473,000,000
Segment profit (loss)	528,000,000	840,000,000	1,709,000,000	2,442,000,000
Depreciation and amortization	333,000,000	374,000,000	981,000,000	1,062,000,000
Interest income	33,000,000	27,000,000	130,000,000	92,000,000
Interest expense	(93,000,000)	(81,000,000)	(288,000,000)	(249,000,000)
Restructuring costs	(74,000,000)	(76,000,000)	(248,000,000)	(418,000,000)
Transaction, separation and integration-related costs	(68,000,000)	(107,000,000)	(226,000,000)	(305,000,000)
Amortization of acquired intangible assets	(146,000,000)	(134,000,000)	(435,000,000)	(401,000,000)
Impairment losses	(53,000,000)	0	(2,940,000,000)	0
Gain on arbitration award	0	0	632,000,000	0
Income (loss) from continuing operations before income taxes	127,000,000	469,000,000	(1,666,000,000)	1,161,000,000
GBS
Segment Reporting Information [Line Items]
Impairment losses			(2,675,000,000)
GIS
Segment Reporting Information [Line Items]
Impairment losses			(265,000,000)
Operating segments
Segment Reporting Information [Line Items]
Revenues	5,021,000,000	5,178,000,000	14,762,000,000	15,473,000,000
Segment profit (loss)	585,000,000	923,000,000	1,893,000,000	2,673,000,000
Depreciation and amortization	305,000,000	347,000,000	899,000,000	969,000,000
Operating segments | GBS
Segment Reporting Information [Line Items]
Revenues	2,359,000,000	2,169,000,000	6,803,000,000	6,493,000,000
Segment profit (loss)	353,000,000	395,000,000	1,078,000,000	1,198,000,000
Depreciation and amortization	61,000,000	23,000,000	128,000,000	59,000,000
Operating segments | GIS
Segment Reporting Information [Line Items]
Revenues	2,662,000,000	3,009,000,000	7,959,000,000	8,980,000,000
Segment profit (loss)	232,000,000	528,000,000	815,000,000	1,475,000,000
Depreciation and amortization	244,000,000	324,000,000	771,000,000	910,000,000
All Other
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Segment profit (loss)	(57,000,000)	(83,000,000)	(184,000,000)	(231,000,000)
Depreciation and amortization	$ 28,000,000	$ 27,000,000	$ 82,000,000	$ 93,000,000