(Change in Benefit Obligation) (Details) (USD $) In Millions, unless otherwise specified	5 Months Ended	12 Months Ended
	Aug. 31, 2013	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Amendments	$ 97	$ 11
Pension Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of period	1,581	1,672	1,581
Service cost		43	48	43
Interest cost		66	63	64
Members’ contributions		5	5
Benefits paid		(56)	(51)
Amendments		(3)	(5)
Curtailments, settlements and special termination benefits		(16)	(8)
Actuarial losses (gains)		296	(5)
Other		(2)	(1)
Currency (gains) losses		(142)	45
Benefit obligation at end of period		1,863	1,672	1,581
Pension Benefits [Member] | Funded Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at end of period		1,558	1,417
Pension Benefits [Member] | Unfunded Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at end of period		305	255
Other Benefits [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of period	234	135	234
Service cost		5	8	10
Interest cost		5	7	10
Members’ contributions		0	0
Benefits paid		(10)	(9)	(8)
Amendments		11	(89)
Curtailments, settlements and special termination benefits		(1)	0
Actuarial losses (gains)		(4)	(15)
Other		0	0
Currency (gains) losses		(2)	(1)
Benefit obligation at end of period		139	135	234
Other Benefits [Member] | Funded Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at end of period		0	0
Other Benefits [Member] | Unfunded Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at end of period		$ 139	$ 135