Segment and Geographic Information - Segment Information (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Revenues	$ 20,753	$ 21,733	$ 7,607
Segment Profit	3,269	2,989	618
Depreciation and amortization	1,429	1,269	570
Amortization of acquired intangible assets	(539)	(526)	(77)
Reconciliation of Consolidated Operating Income to Income Before Taxes [Abstract]
Segment Profit	3,269	2,989	618
Interest income	128	89	35
Interest expense	(334)	(320)	(117)
Restructuring costs	(465)	(789)	(238)
Transaction, separation, and integration-related costs	(401)	(359)	(308)
Amortization of acquired intangible assets	(539)	(526)	(77)
Pension and OPEB actuarial and settlement (losses) gains	(143)	220	(87)
Income (loss) from continuing operations, before taxes	1,515	1,304	(174)
Operating segments
Segment Reporting Information [Line Items]
Revenues	20,753	21,733	7,607
Segment Profit	3,556	3,168	798
Depreciation and amortization	1,302	1,177	506
Reconciliation of Consolidated Operating Income to Income Before Taxes [Abstract]
Segment Profit	3,556	3,168	798
Operating segments | GBS
Segment Reporting Information [Line Items]
Revenues	8,684	9,254	4,173
Segment Profit	1,645	1,525	492
Depreciation and amortization	90	99	107
Reconciliation of Consolidated Operating Income to Income Before Taxes [Abstract]
Segment Profit	1,645	1,525	492
Operating segments | GIS
Segment Reporting Information [Line Items]
Revenues	12,069	12,479	3,434
Segment Profit	1,911	1,643	306
Depreciation and amortization	1,212	1,078	399
Reconciliation of Consolidated Operating Income to Income Before Taxes [Abstract]
Segment Profit	1,911	1,643	306
Corporate
Segment Reporting Information [Line Items]
Revenues	0	0	0
Segment Profit	(287)	(179)	(180)
Depreciation and amortization	127	92	64
Reconciliation of Consolidated Operating Income to Income Before Taxes [Abstract]
Segment Profit	$ (287)	$ (179)	$ (180)