Fair Value Measurements (Tables)

12 Months Ended

Mar. 31, 2015

Fair Value Disclosures [Abstract]

Derivative assets and liabilities measured and recognized at fair value on a recurring basis classified under the appropriate level of the fair value hierarchy

The following tables present our derivative assets and liabilities which were measured and recognized at fair value on a recurring basis classified under the appropriate level of the fair value hierarchy as of March 31, 2015 and March 31, 2014 (in millions).

	March 31,
	2015						2014
	Assets			Liabilities			Assets			Liabilities
Level 2 instruments
Aluminum contracts	$	39		$	(31	)	$	23		$	(36	)
Currency exchange contracts	35			(111		)	28			(23		)
Energy contracts	3			(14		)	4			(1		)
Interest rate swaps	—			(1		)	—			—
Total level 2 instruments	77			(157		)	55			(60		)
Level 3 instruments
Energy contracts	—			(16		)	—			(19		)
Total level 3 instruments	—			(16		)	—			(19		)
Total gross	$	77		$	(173	)	$	55		$	(79	)
Netting adjustment (A)	$	(28	)	$	28		$	(20	)	$	20
Total net	$	49		$	(145	)	$	35		$	(59	)

(A) Amounts represent the impact of legally enforceable master netting agreements that allow the Company to settle positive and negative positions with the same counterparties.

Reconciliation of fair value activity for Level 3 derivative contracts

The following table presents a reconciliation of fair value activity for Level 3 derivative contracts (in millions).

	Level 3 – Derivative Instruments (A)
Balance as of March 31, 2013	$	(27	)
Unrealized gain included in earnings (B)	19
Settlements	(11		)
Balance as of March 31, 2014	$	(19	)
Unrealized gain included in earnings (B)	10
Settlements	(7		)
Balance as of March 31, 2015	$	(16	)

(A)Represents net derivative liabilities.

(B)Included in “Other expense (income), net.”

Estimated fair value of certain financial instruments that are not recorded at fair value on a recurring basis

The table below presents the estimated fair value of certain financial instruments not recorded at fair value on a recurring basis (in millions). The table excludes short-term financial assets and liabilities for which we believe carrying value approximates fair value. The fair value of long-term receivables is based on anticipated cash flows, which approximates carrying value and is classified as Level 2. We value long-term debt using Level 2 inputs. Valuations are based on either market and/or broker ask prices when available or on a standard credit adjusted discounted cash flow model using market observable inputs.

	March 31,
	2015				2014
	Carrying Value		Fair Value		Carrying Value		Fair Value
Assets
Long-term receivables from related parties	$	15	$	15	$	12	$	12
Liabilities
Total debt — third parties (excluding short term borrowings)	$	4,457	$	4,659	$	4,451	$	4,734