Segment Information (Details)	3 Months Ended		6 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) segment	Sep. 30, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			2
Revenues	$ 4,851,000,000	$ 5,013,000,000	$ 9,741,000,000	$ 10,295,000,000
Segment profit (loss)	529,000,000	799,000,000	1,181,000,000	1,602,000,000
Depreciation and amortization	316,000,000	352,000,000	648,000,000	688,000,000
Interest income	67,000,000	33,000,000	97,000,000	65,000,000
Interest expense	(104,000,000)	(83,000,000)	(195,000,000)	(168,000,000)
Restructuring costs	(32,000,000)	(157,000,000)	(174,000,000)	(342,000,000)
Transaction, separation and integration-related costs	(53,000,000)	(128,000,000)	(158,000,000)	(198,000,000)
Amortization of acquired intangible assets	(151,000,000)	(132,000,000)	(289,000,000)	(267,000,000)
Impairment losses	(2,887,000,000)	0	(2,887,000,000)	0
Gain on arbitration award	632,000,000	0	632,000,000	0
(Loss) income from continuing operations before income taxes	(1,999,000,000)	332,000,000	(1,793,000,000)	692,000,000
GBS
Segment Reporting Information [Line Items]
Impairment losses			(2,625,000,000)
GIS
Segment Reporting Information [Line Items]
Impairment losses			(262,000,000)
Operating segments
Segment Reporting Information [Line Items]
Revenues	4,851,000,000	5,013,000,000	9,741,000,000	10,295,000,000
Segment profit (loss)	602,000,000	873,000,000	1,308,000,000	1,750,000,000
Depreciation and amortization	291,000,000	321,000,000	594,000,000	622,000,000
Operating segments | GBS
Segment Reporting Information [Line Items]
Revenues	2,285,000,000	2,111,000,000	4,444,000,000	4,324,000,000
Segment profit (loss)	359,000,000	400,000,000	725,000,000	803,000,000
Depreciation and amortization	39,000,000	16,000,000	67,000,000	36,000,000
Operating segments | GIS
Segment Reporting Information [Line Items]
Revenues	2,566,000,000	2,902,000,000	5,297,000,000	5,971,000,000
Segment profit (loss)	243,000,000	473,000,000	583,000,000	947,000,000
Depreciation and amortization	252,000,000	305,000,000	527,000,000	586,000,000
All Other
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Segment profit (loss)	(73,000,000)	(74,000,000)	(127,000,000)	(148,000,000)
Depreciation and amortization	$ 25,000,000	$ 31,000,000	$ 54,000,000	$ 66,000,000