Share-Based Compensation (Fair Value Assumptions) (Details) - SARs [Member]	12 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Hindalco SARs [Member]
Assumptions used in estimating fair value of SARs
Dividend yield	0.51%	1.14%	0.78%
Hindalco SARs [Member] \| Minimum [Member]
Assumptions used in estimating fair value of SARs
Risk-free interest rate	7.23%	7.75%	8.67%
Volatility	43.00%	39.00%	37.00%
Hindalco SARs [Member] \| Maximum [Member]
Assumptions used in estimating fair value of SARs
Risk-free interest rate	7.68%	7.79%	8.96%
Volatility	44.00%	46.00%	51.00%
Novelis SARs [Member]
Assumptions used in estimating fair value of SARs
Dividend yield	0.00%	0.00%	0.00%
Novelis SARs [Member] \| Minimum [Member]
Assumptions used in estimating fair value of SARs
Risk-free interest rate	0.89%	0.96%	0.96%
Volatility	38.00%	27.00%	28.00%
Novelis SARs [Member] \| Maximum [Member]
Assumptions used in estimating fair value of SARs
Risk-free interest rate	1.39%	1.59%	2.05%
Volatility	41.00%	34.00%	41.00%

No definition available.

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- Definition

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

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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

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