Regulatory Matters (Details) (Alabama Gas Corporation, USD $)	0 Months Ended				3 Months Ended		6 Months Ended
	Jan. 02, 2014	Dec. 01, 2013	Nov. 05, 2013	Dec. 01, 2012	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Regulatory Matters [Line Items]
Performance based adjustment on adjusting point			5.00%
Revenue reductions (increase) of rate adjustments	$ 8,500,000	$ (10,300,000)		$ (7,800,000)	$ 4,000,000	$ 3,800,000	$ 20,300,000	$ 6,300,000
Equity upon which a return will be permitted			56.50%
Approved increase			1.75%
Increase to revenue due to O&M expense below index range					1,000,000
Enhanced Stability Reserve refund period					9 years
Enhanced Stability Reserve amortization period					5 years
Enhanced Stability Reserve, amortization expense							660,000
APSC Approved Expension of ESR, November 1, 2010
Regulatory Matters [Line Items]
Large commercial and industrial customer budget minimum amount charged to Enhanced Stability Reserve							350,000
Force Majeure Event Costs | APSC Approved Expension of ESR, November 1, 2010
Regulatory Matters [Line Items]
Extraordinary operating and maintenance expenses minimum amount charged to Enhanced Stability Reserve							275,000
Force Majeure Events Costs | APSC Approved Expension of ESR, November 1, 2010
Regulatory Matters [Line Items]
Extraordinary operating and maintenance expenses minimum amount charged to Enhanced Stability Reserve							412,500
Self Insurance Costs | APSC Approved Expension of ESR, November 1, 2010
Regulatory Matters [Line Items]
Extraordinary operating and maintenance expenses minimum amount charged to Enhanced Stability Reserve					$ 1,000,000
Minimum
Regulatory Matters [Line Items]
Allowed return on average common equity					13.15%
Maximum
Regulatory Matters [Line Items]
Allowed return on average common equity					13.65%
Rate increases as percentage of prior year revenues					4.00%
APSC
Regulatory Matters [Line Items]
Adjusting point			10.80%
APSC | Minimum
Regulatory Matters [Line Items]
Approved return on equity			10.50%
APSC | Maximum
Regulatory Matters [Line Items]
Approved return on equity			10.95%