Investment in and Advances to Non-Consolidated Affiliates and Related Party Transactions (Details Textual) € in Millions	1 Months Ended	12 Months Ended
	Apr. 30, 2014 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Mar. 31, 2017 EUR (€)
Schedule of Equity Method Investments [Line Items]
Difference between carrying amount and underlying equity		$ 370,000,000
Accounts receivable - related parties		60,000,000	$ 59,000,000
Alunorf [Member]
Schedule of Equity Method Investments [Line Items]
Interest income on loan (less than)		1,000,000
Allowance for loan loss		$ 0
Equity Method Investee [Member]
Schedule of Equity Method Investments [Line Items]
Guarantee as percentage of outstanding debt		50.00%
Maximum exposure for gauranteed obligation | €					€ 6
Accounts receivable - related parties		$ 60,000,000	59,000,000
Equity Method Investee [Member] | Supplemental Employee Retirement Plan [Member]
Schedule of Equity Method Investments [Line Items]
Maximum exposure for gauranteed obligation		2,000,000
Hindalco [Member]
Schedule of Equity Method Investments [Line Items]
Revenue from related party		1,000,000	1,000,000	$ 1,000,000
Parent [Member]
Schedule of Equity Method Investments [Line Items]
Accounts receivable - related parties			1,000,000
Related Party Transaction, Purchases from Related Party		$ 3,000,000	$ 5,000,000
Return of capital to shareholder	$ 250,000,000