Basis of Presentation (Details) (Alabama Gas Corporation, USD $) In Millions, except Per Share data	3 Months Ended
	Mar. 31, 2010
Overstatement to allowance for doubtful accounts
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Quantifying Misstatement in Current Year Financial Statements, Amount	$ 3.0
Overstatement of net income
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Quantifying Misstatement in Current Year Financial Statements, Amount	$ 0.6
Earnings Per Share, Diluted
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Quantifying Misstatement in Current Year Financial Statements, Per Share	$ 0.01