Derivatives (Details Textuals) (USD $) In Millions, unless otherwise specified	6 Months Ended
Jun. 30, 2012
Derivative [Line Items]
Unrealized derivative fair value related to cash flow hedges to be reclassfied within 12 months	$ 0
Cash Flow Liquid Swap [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Price Risk Fair Value Hedging Instruments	1.7
Cash Flow Gas Swap [Member]
Derivative [Line Items]
Maximum counterparty loss	13.5
Maximum counterparty loss with netting feature	12.1
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	$ 1.6

The amount recognized in earnings related to the change in fair value during the period of derivative or nonderivative instruments designated as fair value hedging instruments.

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- Details

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- Definition

The estimated net amount of unrealized gains or losses on price risk cash flow hedges as of the balance sheet date expected to be reclassified to earnings within the next twelve months.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 45

-Subparagraph b(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 815

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6887037&loc=d3e80748-113994

+ Details

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- Definition

Amount of unrealized gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of price risk derivatives instruments designated as fair value hedging instruments, as offset by the gain (loss) on the hedged item to the extent that the fair value hedge is determined to be effective.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 45

-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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5618551-113959

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5624171-113959

+ Details

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- Definition

The maximum potential exposure to credit losses on derivative contracts.

+ References

No definition available.

+ Details

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- Definition

The net potential exposure to credit losses on derivative contracts

+ References

No definition available.

+ Details

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Period Type:	instant