Gas Stored Underground and Gas Receivables and Payables (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2011	Dec. 31, 2010
Gas Stored Underground and Gas Receivables and Payables [Abstract]
Gas held for storage on behalf of customers (TBtu)	74.9	82.9
Average market price of gas assumed during the period (per MMBtu)	3.82
Market value of gas held on behalf of customers	$ 286.1
The volume of gas owed to the operating subsidiaries due to gas imbalances and gas loaned under PAL agreements (TBtu)	8.5	13.0
Market value of gas owed to operating subsidiaries due to gas imbalances and gas loaned under PAL agreements	$ 32.5

Average market price of natural gas assumed during the month prior to the balance sheet date and used to calculate the total market value of (1) gas held in storage on behalf of customers, and (2) gas owed to operating subsidiaries due to gas imbalances and gas loaned under parking and lending agreements.

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- Definition

Amount of natural gas stored underground as of balance sheet date, in depleted gas reservoirs, aquifers, or salt caverns to meet seasonal and peak load demands, and also as insurance against unforeseen supply disruptions, which is owned by third parties and not recorded on the Company's Condensed Consolidated Balance Sheet.

+ Details

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- Definition

The value of gas balancing asset or liability as of the end of the period.

+ Details

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- Details

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- Definition

The market value of gas held in storage on behalf of its customers. This is not recognized in the financial statements because the Partnership does not own the gas - it is a market risk, however.

+ Details

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- Definition

The amount of the gas imbalance in terms of units of measure (Mcf) as of the end of the period.

+ References

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

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 90-22

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 10

-Section S99

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6949603&loc=d3e512571-122862

+ Details

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