Revenue - Change in Contract Liabilities (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2018
Change In Contract With Customer, Liability [Roll Forward]
Balance, beginning of period	$ 1,881	$ 2,053
Deferred revenue	569	1,172
Recognition of deferred revenue	(665)	(1,307)
Currency translation adjustment	(19)	(137)
Other	(23)	(38)
Balance, end of period	1,743	1,743
Calculated under Revenue Guidance in Effect before Topic 606
Change In Contract With Customer, Liability [Roll Forward]
Balance, beginning of period	0	2,434
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)