Concentration of Credit Risk (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2011	Sep. 30, 2010
Nonregulated Segment Credit Exposure [Abstract]
Investment grade	54.00%	58.00%
Non-investment grade	46.00%	42.00%
Total	100.00%	100.00%
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	16
Non-investment grade counterparties	1,081
Total	$ 1,097

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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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- 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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- Details

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- Definition

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

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- Definition

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

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- Definition

Total percentage of AEM customers.

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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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