Gas Reserves and Other Investments (details) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2011
Gas Reserves [Abstract]
Term Of Gas Reserves Contract In Years	30
Peak Volume Of Gas Reserves Contract	13.00%
Gas Reserves Average Volume Over First Ten Years	8 to 10 percent
Annual Gas Reserves Investment	$45 million to $55 million
Total Expected Gas Reserves Investment	$ 250.00
Maximum Regulatory Variance Exposure	10.00
Changes In Fair Value Deferred As Income Statement For Contracts Not Qualifying For Hedge Accounting And To Other Comprehensive Income For Contracts Qualifying For Hedge Accounting	10.00%
Net Gas Reserves Investment	20.40
Deferred Taxes Related To Gas Reserves	10.10
Palomar [Abstract]
Equity Method Investment Ownership Percentage	50.00%
Palomar West Zone Impairment	0.30
Equity Method Investment Underlying Equity In Net Assets	14.40
Equity Method Investment Exposure	$ 14.10

The expected investment range stated in dollars for each of the first five years under the Encana gas reserves contract.

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- Definition

Percentage of gains or losses that are not deferred as regulatory assets or liabilities. This percentage impact earnings.

+ Details

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- Definition

Deferred taxes related to gas reserves

+ Details

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- Definition

The exposure to the parent related to an equity contribution (Palomar) net of other appicable balance sheet items.

+ Details

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- Details

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- Definition

The anticipated average volume as a percentage of our annual utility requirements over first ten years of the Encana gas reserves contract.

+ Details

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- Definition

Maximum exposure for the Encana gas reserves deal as a variance from the Purchased Gas Adjustment mechanism embedded rates.

+ Details

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- Definition

Gas reserves investment net of amortization and deferred taxes.

+ Details

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- Details

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- Definition

Impairment write-off of Palomar west zone assets

+ Details

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- Definition

Discloses the anticipated peak volume of gas reserves contract as a percentage. This peak volume is anticipated to occur in the 2015-2016 gas year.

+ Details

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- Definition

Term of the Encana gas reserves contract in years

+ Details

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- Definition

Total expected gas reserves investment for the Encana gas reserves contract.

+ Details

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 159

-Paragraph 18

-Subparagraph f

-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 AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 20

-Subparagraph a (1)

-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 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

+ Details

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- Definition

This item represents the entity's ownership percentage in the investee multiplied by the investee's total equity.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (a)(3)

-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

+ Details

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