Investment in and Advances to Non-Consolidated Affiliates and Related Party Transactions (Results of Operations of Equity Method Affiliates) (Details) (Equity Method Investments [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Equity Method Investments [Member]
Summary of the share of the condensed results of operations of equity method affiliates
Net sales	$ 524	$ 550	$ 489
Costs and expenses related to net sales	527	543	488
Provision for taxes on income	0	4	2
Net (loss) income	(3)	3	(1)
Purchase of tolling services from Aluminium Norf GmbH (Alunorf)	$ 261	$ 275	$ 244