Investment in and Advances to Non-Consolidated Affiliates and Related Party Transactions (Details Textual)	1 Months Ended	12 Months Ended		12 Months Ended				12 Months Ended			1 Months Ended
	Aug. 31, 2013 USD ($)	Mar. 31, 2014 USD ($)	Mar. 31, 2015 USD ($)	Mar. 31, 2015 Alunorf [Member] USD ($)	Mar. 31, 2015 Alunorf [Member] EUR (€)	Mar. 31, 2014 Alunorf [Member] USD ($)	Mar. 31, 2015 Alunorf [Member] Supplemental Employee Retirement Plan [Member] USD ($)	Mar. 31, 2015 Hindalco [Member] USD ($)	Mar. 31, 2014 Hindalco [Member] USD ($)	Mar. 31, 2013 Hindalco [Member] USD ($)	Mar. 31, 2014 AV Metals, Inc. [Member] USD ($)
Schedule of Equity Method Investments [Line Items]
Difference between carrying amount and underlying equity			$ 337,000,000
Interest income on loan (less than)				1,000,000
Allowance for loan loss				0		0
Guarantee as percentage of outstanding debt				50.00%
Maximum exposure for gauranteed obligation					6,000,000		2,000,000
Revenue from related party								1,000,000	1,000,000	5,000,000
Proceeds from sale of bauxite mining rights and certain alumina assets and liabilities	8,000,000								8,000,000
Accounts receivable - related parties		54,000,000	53,000,000					1,000,000	1,000,000
Return of capital to shareholder		$ 250,000,000									$ 250,000,000