Share-Based Compensation (Details 3) (SARs [Member])	6 Months Ended
Sep. 30, 2014	Sep. 30, 2013
Hindalco SARs [Member]
Assumptions used in estimating fair value of SARs
Dividend yield	0.64%	1.25%
Hindalco SARs [Member] \| Minimum [Member]
Assumptions used in estimating fair value of SARs
Risk-free interest rate	8.43%	8.72%
Volatility	41.00%	36.00%
Hindalco SARs [Member] \| Maximum [Member]
Assumptions used in estimating fair value of SARs
Risk-free interest rate	8.73%	9.07%
Volatility	54.00%	51.00%
Novelis SARs [Member]
Assumptions used in estimating fair value of SARs
Dividend yield	0.00%	0.00%
Novelis SARs [Member] \| Minimum [Member]
Assumptions used in estimating fair value of SARs
Risk-free interest rate	1.29%	0.89%
Volatility	29.00%	29.00%
Novelis SARs [Member] \| Maximum [Member]
Assumptions used in estimating fair value of SARs
Risk-free interest rate	2.13%	1.90%
Volatility	43.00%	41.00%

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (f)(2)(iii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (f)(2)(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (f)(2)(iv)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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