Intangible Assets - Summary of Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2021	Mar. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 8,572	$ 8,465
Accumulated Amortization	4,997	4,422
Net Carrying Value	3,575	4,043
Software
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	4,129	4,014
Accumulated Amortization	3,013	2,733
Net Carrying Value	1,116	1,281
Customer related intangible assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	4,173	4,212
Accumulated Amortization	1,910	1,641
Net Carrying Value	2,263	2,571
Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	270	239
Accumulated Amortization	74	48
Net Carrying Value	$ 196	$ 191