Commitments and Contingencies (Environmental Matters) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 pit
Alabama Gas Corporation
Site Contingency [Line Items]
Chain of title, manufactured gas plant sites	9
Chain of title, manufactured gas distribution sites	5
Sites owned by Alagasco | Alabama Gas Corporation
Site Contingency [Line Items]
Chain of title, manufactured gas plant sites	4
Chain of title, manufactured gas distribution sites	1
Mitchell County, Texas
Site Contingency [Line Items]
Number of reserves pits	9
Expected environmental remediation costs	$ 2.1
Cost incurred, environmental remediation	1.9
Environmental remediation reserve	$ 0.2