Regulatory Matters (Details) (Alabama Gas Corporation, USD $)	0 Months Ended			3 Months Ended						0 Months Ended	12 Months Ended	0 Months Ended	3 Months Ended	12 Months Ended	0 Months Ended
	Jan. 02, 2014	Dec. 01, 2013	Dec. 01, 2012	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 APSC Approved Expension of ESR, November 1, 2010	Mar. 31, 2014 APSC Approved Expension of ESR, November 1, 2010 Self Insurance Costs	Mar. 31, 2014 APSC Approved Expension of ESR, November 1, 2010 Force Majeure Event Costs	Mar. 31, 2014 APSC Approved Expension of ESR, November 1, 2010 Force Majeure Events Costs	Jan. 02, 2014 APSC	Dec. 31, 2013 Minimum	Jan. 02, 2014 Minimum APSC	Mar. 31, 2014 Maximum	Dec. 31, 2013 Maximum	Jan. 02, 2014 Maximum APSC
Regulatory Matters [Line Items]
Approved return on equity												10.50%			10.95%
Adjusting point										10.80%
Allowed return on average common equity											13.15%			13.65%
Performance based adjustment on adjusting point	0.05%
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)	$ 16,200,000	$ 2,400,000
Equity upon which a return will be permitted	56.50%
Approved increase	1.75%
Extraordinary operating and maintenance expenses minimum amount charged to Enhanced Stability Reserve							1,000,000	275,000	412,500
Large commercial and industrial customer budget minimum amount charged to Enhanced Stability Reserve						350,000
Enhanced Stability Reserve refund period				9 years
Enhanced Stability Reserve amortization period				5 years
Enhanced Stability Reserve, amortization expense				$ 660,000