Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Interest rate swaps
Liabilities:
Derivative Liabilities		$ 100
Interest rate swaps \| Maximum
Liabilities:
Derivative Liabilities	100
Commodity contracts
Derivative assets (liabilities)
Net LIABILITY	(7,106)	(36)
Commodity contracts \| Prepaid expenses and other current assets
Derivative assets (liabilities)
Net LIABILITY	5,551
Commodity contracts \| Other noncurrent assets
Derivative assets (liabilities)
Net LIABILITY	44
Commodity contracts \| Accrued expenses and other payables
Derivative assets (liabilities)
Net LIABILITY	(12,701)	(36)
Recurring \| Commodity contracts
Assets:
Derivative Assets	10,858
Liabilities:
Derivative Liabilities	(16,604)	(36)
Netting of counterparty contracts, assets	(3,503)
Netting of counterparty contracts, liabilities	3,503
Cash collateral provided or held, assets	(1,760)
Cash collateral provided or held, liabilities	400
Commodity contracts reported on consolidated balance sheet, assets	5,595
Commodity contracts reported on consolidated balance sheet, liabilities	(12,701)	(36)
Recurring \| Level 1 \| Commodity contracts
Assets:
Derivative Assets	947
Liabilities:
Derivative Liabilities	(3,324)
Recurring \| Level 2 \| Commodity contracts
Assets:
Derivative Assets	9,911
Liabilities:
Derivative Liabilities	$ (13,280)	$ (36)

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Fair value of liability associated with derivative asset, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 205G

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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The amount of the obligation to return cash collateral under master netting arrangements that have not been offset against net derivative instrument positions.

+ References

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-Publisher FASB

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The amount of the right to reclaim cash collateral under master netting arrangements that have not been offset against net derivative instrument positions.

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Fair value of derivative liability, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

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Fair value of the assets less the liabilities of a derivative or group of derivatives.

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Fair value as of the balance sheet date of derivative instrument not designated as hedging instrument and classified as an asset.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Fair value as of the balance sheet date of derivative instrument not designated as hedging instrument and classified as a liability.

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