Concentration of Credit Risk (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Sep. 30, 2011
Nonregulated Segment Credit Exposure [Abstract]
Investment grade	60.00%	54.00%
Non-investment grade	40.00%	46.00%
Total	100.00%	100.00%
Counterparty Credit Exposure [Line Items]
Investment grade counterparties	$ 4
Non-investment grade counterparties	0
Total	4
Natural Gas Distribution Segment [Member]
Counterparty Credit Exposure [Line Items]
Investment grade counterparties	0
Non-investment grade counterparties	0
Total	0
Nonregulated Segment [Member]
Counterparty Credit Exposure [Line Items]
Investment grade counterparties	4
Non-investment grade counterparties	0
Total	$ 4

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The financial instrument counterparty credit exposure based upon the unrealized fair value of our financial instruments that represent assets as of the balance sheet date with our investment grade counterparties. Investment grade counterparties have minimum credit ratings of BBB-, assigned by S&P or Baa3, assigned by Moody's.

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No definition available.

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- Definition

The financial instrument counterparty credit exposure based upon the unrealized fair value of our financial instruments that represent assets as of the balance sheet date with our non-investment grade counterparties. Non-investment grade counterparties are composed of counterparties that are below investment grade or that have not been assigned an internal investment grade rating due to the short-term nature of the contracts associated with that counterparty.

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No definition available.

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- Details

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- Definition

The percentage of AEM customers, including affiliate customers that are rated as investment grade.

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No definition available.

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- Definition

The percentage of AEM customers, including affiliate customers that are rated as non-investment grade.

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No definition available.

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- Definition

Total percentage of AEM customers.

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No definition available.

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- Definition

The total financial instrument counterparty credit exposure based upon the unrealized fair value of our financial instruments that represent assets as of the balance sheet date.

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No definition available.

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