Revenue - Change in Contract Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Change In Contract With Customer, Liability [Roll Forward]
Balance, beginning of period	$ 1,886	$ 2,053
Deferred revenue	2,910	2,681
Recognition of deferred revenue	(2,925)	(2,664)
Currency translation adjustment	(48)	(167)
Other	(67)	(17)
Balance, end of period	1,756	1,886
Calculated under Revenue Guidance in Effect before Topic 606
Change In Contract With Customer, Liability [Roll Forward]
Balance, beginning of period	0	2,434
Balance, end of period		0
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Change In Contract With Customer, Liability [Roll Forward]
Balance, beginning of period	$ 0	(381)
Balance, end of period		$ 0