Debt (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Mar. 31, 2014
Debt Instrument [Line Items]
Long-term debt, Carrying Value	$ 4,432		$ 4,451
Total debt	5,494		5,197
Total debt, Unamortized Carrying Value Adjustment	(18)		(23)
Total debt, carrying value	5,476		5,174
Short-term borrowings	(1,044)		(723)
Current portion of long-term debt	(92)		(92)
Long-term debt, net of current portion, Principal	4,358		4,382
Long-term debt, net of current portion, Carrying Value	4,340		4,359
Floating Rate Term Loan Facility, due March 2017 [Member]
Debt Instrument [Line Items]
Interest Rates	3.75%	[1]
Long-term debt, Principal	1,740		1,749
Long-term debt, Unamortized Carrying Value Adjustments	(16)	[2]	(20)	[2]
Long-term debt, Carrying Value	1,724		1,729
8.375% Senior Notes, due December 2017 [Member]
Debt Instrument [Line Items]
Interest Rates	8.375%	[1]
Long-term debt, Principal	1,100		1,100
Long-term debt, Unamortized Carrying Value Adjustments	0		0
Long-term debt, Carrying Value	1,100		1,100
8.75% Senior Notes, due December 2020 [Member]
Debt Instrument [Line Items]
Interest Rates	8.75%	[1]
Long-term debt, Principal	1,400		1,400
Long-term debt, Unamortized Carrying Value Adjustments	0		0
Long-term debt, Carrying Value	1,400		1,400
Capital Lease Obligation due July 2017 [Member]
Debt Instrument [Line Items]
Interest Rates	3.64%	[1]
Long-term debt, Principal	10		11
Long-term debt, Unamortized Carrying Value Adjustments	0		0
Long-term debt, Carrying Value	10		11
Korean Loans due December 2014 through 2015 [Member] | KOREA, REPUBLIC OF
Debt Instrument [Line Items]
Interest Rates	3.34%	[1]
Long-term debt, Principal	154		155
Long-term debt, Unamortized Carrying Value Adjustments	0		0
Long-term debt, Carrying Value	154		155
Capital Lease Obligation, due December 2019 [Member] | Switzerland [Member]
Debt Instrument [Line Items]
Interest Rates	7.50%	[1]
Capital lease obligation, Principal	31		36
Capital lease obligation, Unamortized Carrying Value Adjustments	(1)	[3]	(1)	[3]
Capital lease obligation, Carrying Value	30		35
BNDES Loans, due March 2015 through April 2021 [Member] | Brazil [Member]
Debt Instrument [Line Items]
Interest Rates	5.58%	[1]
Long-term debt, Principal	10		13
Long-term debt, Unamortized Carrying Value Adjustments	(1)	[4]	(2)	[4]
Long-term debt, Carrying Value	9		11
Other Debt, due through December 2020 [Member]
Debt Instrument [Line Items]
Interest Rates	5.85%	[1]
Long-term debt, Principal	5		10
Long-term debt, Unamortized Carrying Value Adjustments	0		0
Long-term debt, Carrying Value	5		10
Short term borrowings [Member]
Debt Instrument [Line Items]
Interest Rates	3.67%	[1]
Long-term debt, Unamortized Carrying Value Adjustments	0	[2]	0	[2]
Short-term borrowings	$ (1,044)		$ (723)

[1] Interest rates are the fixed or variable rates as specified in the debt instruments (not the effective interest rate) as of September 30, 2014, and therefore, exclude the effects of related interest rate swaps, accretion/amortization of fair value adjustments as a result of purchase accounting in connection with Hindalco's purchase of Novelis and accretion/amortization of debt issuance costs related to the debt exchange completed in fiscal 2009 and the series of refinancing transactions and additional borrowings we completed in fiscal 2011, 2012 and 2013. We present stated rates of interest because they reflect the rate at which cash will be paid for future debt service.

[2] Debt existing at the time of Hindalco's purchase of Novelis was recorded at fair value. In connection with a series of refinancing transactions, a portion of the historical fair value adjustments was allocated to the Term Loan Facility, resulting in carrying value adjustments on this debt obligation. The unamortized carrying value also includes an issuance discount.

[3] Debt existing at the time of Hindalco's purchase of Novelis was recorded at fair value resulting in carrying value adjustments to our capital lease obligations in Novelis Switzerland.

[4] The unamortized carrying value includes issuance discounts related to the difference resulting from the contractual rates of interest specified in the instruments that are lower than the market rates of interest upon issuance.