Redeemable Noncontrolling Interests and Noncontrolling Interests - Schedule of Changes in Redeemable Noncontrolling Interests and Noncontrolling Interests (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Noncontrolling Interests [Roll Forward]
Beginning balance			$ 178
Net income attributable to noncontrolling interests	$ 58	$ 13	169	$ 48
Other comprehensive income (loss)	12		161
Ending balance	238		238
Redeemable Noncontrolling Interests
Beginning balance			1,327
Other comprehensive income (loss)	12		161
Ending balance	1,435		1,435
Noncontrolling Interest
Noncontrolling Interests [Roll Forward]
Beginning balance			178	84
Net income attributable to noncontrolling interests	46	3	137	15
Other comprehensive income (loss)			0	0
Payments to noncontrolling interests			(73)
Exercises of Put Right			0
Purchase of noncontrolling interests				93
Other			(4)	(32)
Ending balance	238	160	238	160
Redeemable Noncontrolling Interests
Other comprehensive income (loss)			0	0
Exercises of Put Right			0
Purchase of noncontrolling interests				93
Other			(4)	(32)
Redeemable Noncontrolling Interest
Noncontrolling Interests [Roll Forward]
Other comprehensive income (loss)			161	(95)
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			32	33
Other comprehensive income (loss)			161	(95)
Reclassification of recurring compensation to other accrued liabilities			(32)	(33)
Exercises of Put Right			(53)
Purchase of noncontrolling interests				0
Other			0	0
Ending balance	$ 1,435	$ 1,311	$ 1,435	$ 1,311