Redeemable Noncontrolling Interests and Noncontrolling Interests - Schedule of Changes in Redeemable Noncontrolling Interests and Noncontrolling Interests (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Noncontrolling Interests [Roll Forward]
Beginning balance			$ 178
Net income attributable to noncontrolling interests	$ 55	$ 17	111	$ 35
Other comprehensive income (loss)	33		149
Ending balance	219		219
Redeemable Noncontrolling Interests
Beginning balance			1,327
Other comprehensive income (loss)	33		149
Ending balance	1,423		1,423
Noncontrolling Interest
Noncontrolling Interests [Roll Forward]
Beginning balance			178	84
Net income attributable to noncontrolling interests	44	5	91	12
Other comprehensive income (loss)			0	0
Payments to noncontrolling interests			(47)
Exercises of Put Right			0
Purchase of noncontrolling interests				85
Other			(3)	(7)
Ending balance	219	174	219	174
Redeemable Noncontrolling Interests
Other comprehensive income (loss)			0	0
Exercises of Put Right			0
Purchase of noncontrolling interests				85
Other			(3)	(7)
Redeemable Noncontrolling Interest
Noncontrolling Interests [Roll Forward]
Other comprehensive income (loss)			149	(65)
Payments to noncontrolling interests			0
Exercises of Put Right			(53)
Purchase of noncontrolling interests				0
Other			0	0
Redeemable Noncontrolling Interests
Beginning balance			1,327	1,406
Net income attributable to noncontrolling interests			20	23
Other comprehensive income (loss)			149	(65)
Reclassification of recurring compensation to other accrued liabilities			(20)	(23)
Exercises of Put Right			(53)
Purchase of noncontrolling interests				0
Other			0	0
Ending balance	$ 1,423	$ 1,341	$ 1,423	$ 1,341