Segment and Geographic Information - Segment Information (Details) $ in Millions	12 Months Ended
	Mar. 31, 2021 USD ($) segment	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of reporting segments | segment	2
Revenues	$ 17,729	$ 19,577	$ 20,753
Segment Profit	1,102	2,061	3,269
Depreciation and amortization	1,440	1,359	1,429
Amortization of acquired intangible assets	530	583	539
Reconciliation of Consolidated Operating Income to Income Before Taxes [Abstract]
Segment Profit	1,102	2,061	3,269
Interest income	98	165	128
Interest expense	(361)	(383)	(334)
Restructuring costs	(551)	(252)	(465)
Transaction, separation and integration-related costs	(358)	(318)	(401)
Amortization of acquired intangibles	(530)	(583)	(539)
Gains on dispositions	2,004	0	0
Pension and OPEB actuarial and settlement (losses) gains	(519)	244	(143)
Debt extinguishment cost	(41)	0	0
Impairment losses	(190)	(6,794)	0
Gain on arbitration award	0	632	0
Income (loss) from continuing operations, before taxes	654	(5,228)	1,515
Operating segments
Segment Reporting Information [Line Items]
Revenues	17,729	19,577	20,753
Segment Profit	1,365	2,308	3,556
Depreciation and amortization	1,334	1,250	1,302
Reconciliation of Consolidated Operating Income to Income Before Taxes [Abstract]
Segment Profit	1,365	2,308	3,556
Operating segments | GBS
Segment Reporting Information [Line Items]
Revenues	8,336	9,111	8,684
Segment Profit	1,120	1,301	1,645
Depreciation and amortization	212	199	90
Reconciliation of Consolidated Operating Income to Income Before Taxes [Abstract]
Segment Profit	1,120	1,301	1,645
Operating segments | GIS
Segment Reporting Information [Line Items]
Revenues	9,393	10,466	12,069
Segment Profit	245	1,007	1,911
Depreciation and amortization	1,122	1,051	1,212
Reconciliation of Consolidated Operating Income to Income Before Taxes [Abstract]
Segment Profit	245	1,007	1,911
All Other
Segment Reporting Information [Line Items]
Revenues	0	0	0
Segment Profit	(263)	(247)	(287)
Depreciation and amortization	106	109	127
Reconciliation of Consolidated Operating Income to Income Before Taxes [Abstract]
Segment Profit	$ (263)	$ (247)	$ (287)