Regulatory Matters (Details) (USD $)	12 Months Ended	0 Months Ended		1 Months Ended			12 Months Ended					12 Months Ended				0 Months Ended	12 Months Ended	0 Months Ended	12 Months Ended	0 Months Ended
	Dec. 31, 2013	Jan. 02, 2014 Subsequent Event	Dec. 20, 2013 Alabama Gas Corporation	Dec. 31, 2013 Alabama Gas Corporation	Dec. 31, 2012 Alabama Gas Corporation	Dec. 31, 2011 Alabama Gas Corporation	Dec. 31, 2013 Alabama Gas Corporation	Dec. 31, 2012 Alabama Gas Corporation	Dec. 31, 2011 Alabama Gas Corporation	Dec. 31, 2013 Alabama Gas Corporation Municipal gas distribution systems	Dec. 31, 2012 Alabama Gas Corporation Municipal gas distribution systems	Dec. 31, 2013 Alabama Gas Corporation APSC Approved Expension of ESR, November 1, 2010	Dec. 31, 2013 Alabama Gas Corporation APSC Approved Expension of ESR, November 1, 2010 Force Majeure Event Costs	Dec. 31, 2013 Alabama Gas Corporation APSC Approved Expension of ESR, November 1, 2010 Force Majeure Events Costs	Dec. 31, 2013 Alabama Gas Corporation APSC Approved Expension of ESR, November 1, 2010 Self Insurance Costs	Dec. 20, 2013 Alabama Gas Corporation Alabama Public Service Commission	Dec. 31, 2013 Minimum Alabama Gas Corporation	Dec. 20, 2013 Minimum Alabama Gas Corporation Alabama Public Service Commission	Dec. 31, 2013 Maximum Alabama Gas Corporation	Dec. 20, 2013 Maximum Alabama Gas Corporation Alabama Public Service Commission
Regulatory Matters [Line Items]
Approved return on equity																		10.50%		10.95%
Adjusting point																10.80%
Performance based adjustments on adjusting point			500.00%
Percentage of equity which return is permitted			56.50%
Increase (decrease) in approved rate			1.75%
Allowed return on average common equity																	13.15%		13.65%
Rate increases as percentage of prior year revenues																			4.00%
Revenue reductions (increase) of rate adjustments		$ 8,500,000		$ (10,300,000)	$ (7,800,000)	$ (13,000,000)	$ 10,600,000	$ 6,300,000	$ 6,700,000
Limitation on return on equity as percentage of total capitalization																			55.00%
Adjustment requirement threshold for return on equity as percentage of operations and maintenance expenses to consumer price index							0.75
Extraordinary Operating and maintenance expenses, minimum amount, charged to enhanced stability reserve													275,000	412,500	1,000,000
Negative revenue variance, large commercial and industrial customer budget, minimum amount, charged to enhanced stability reserve												350,000
Amortization expense, enhanced stability reserve, annual amount							660,000
Municipal gas distribution systems, weighted average remaining life (in years)	13 years
Municipal gas distribution systems, net acquisition adjustments										$ 3,200,000	$ 3,800,000