Commitments and Contingencies (Details) - Environmental Matters (Alabama Gas Corporation, USD $) In Millions	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2011
Alabama Gas Corporation
Site Contingency [Line Items]
Environmental Remediation Estimated Cost	$ 4.8
Environmental Remediation Expense	0.6	3.6
Accrual for Environmental Loss Contingencies	$ 0.6	$ 0.6

The charge against earnings in the period for known or estimated future costs arising from requirements to perform environmental remediation activities.

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

-Publisher AICPA

-Name Statement of Position (SOP)

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-Name Emerging Issues Task Force (EITF)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 4: http://www.xbrl.org/2003/role/presentationRef

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

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-Name Statement of Financial Accounting Standard (FAS)

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Reference 7: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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+ Details