Financial Instruments and Commodity Contracts (Details 1) (Aluminum forward purchase contracts [Member], Fair value hedging [Member], Designated as hedging instrument [Member], USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Aluminum forward purchase contracts [Member] | Fair value hedging [Member] | Designated as hedging instrument [Member]
Derivative [Line Items]
Fair Value Hedges of Metal Price Risk, Derivative Contracts	$ 0		$ 2		$ 1		$ (1)
Fair Value Hedges of Metal Price Risk, Designated Hedged Items	0		(2)		(1)		1
Net Ineffectiveness	$ 0	[1]	$ 0	[1]	$ 0	[1]	$ 0	[1]

[1] Effective portion is recorded in "Net sales" and net ineffectiveness in "Other expense (income), net"