Redeemable Noncontrolling Interests and Noncontrolling Interests - Schedule of Changes in Noncontrolling Interests and Redeemable Noncontrolling Interest (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance	$ 253
Net income attributable to noncontrolling interests	221	$ 230	$ 83
Other comprehensive income	(66)	185
Ending balance	193	253
Redeemable Noncontrolling Interest, Beginning balance	1,459
Payments to noncontrolling interests	(184)	(98)
Redeemable Noncontrolling Interest, Ending balance	1,393	1,459
Noncontrolling interests
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance	253	178
Net income attributable to noncontrolling interests	176	187
Other comprehensive income	0	0
Payments to noncontrolling interests		(98)
Other	(52)	(14)
Ending balance	193	253	178
Payments to noncontrolling interests	(184)	(98)
Other	(52)	(14)
Redeemable Noncontrolling Interests
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Other comprehensive income	(66)	185
Payments to noncontrolling interests		0
Exercises of Put Right		53
Other	0	0
Redeemable Noncontrolling Interest, Beginning balance	1,459	1,327
Net income attributable to noncontrolling interests	45	43
Reclassification of recurring compensation to other accrued liabilities	(45)	(43)
Payments to noncontrolling interests	0
Other	0	0
Redeemable Noncontrolling Interest, Ending balance	$ 1,393	$ 1,459	$ 1,327