Dispositions of Properties Narrative (Details) (Alabama Gas Corporation, USD $)	6 Months Ended	1 Months Ended	3 Months Ended
Jun. 30, 2014	Jun. 30, 2013	Aug. 31, 2013 Birmingham Metro Operations Center	Jun. 30, 2014 Birmingham Metro Operations Center	Jun. 30, 2014 Tuscaloosa
Gas and Oil Acreage [Line Items]
Gain on sale of assets	$ 703,000	$ 0	$ 10,900,000		$ 700,000
Sale price of property				$ 13,800,000
Lease back period after sale				20 months

Amount of gain (loss) on sale or disposal of property, plant and equipment assets, including oil and gas property and timber property.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration