Organization and Basis of Presentation - Discontinued Operations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (Loss) from Discontinued Operations	$ (4,799)	$ 645	$ 32,870	$ 48,918
Income (Loss) From Discontinued Operations	(4,799)	645	33,920	48,918
Energen Corporation
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (Loss) from Discontinued Operations	97	2,453	(1,029)	4,451
Alabama Gas Corporation
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Alagasco net income (loss)	(615)	(704)	42,413	46,518
Depreciation, depletion and amortization	(153)	(147)	(305)	(294)
General and administrative	687	1,724	1,627	3,578
Interest expense	(7,190)	(3,288)	(12,977)	(6,109)
Other income	(228)	(64)	(347)	(473)
Income tax expense (benefit)	2,603	671	4,538	1,247
Income (Loss) from Discontinued Operations	$ (4,896)	$ (1,808)	$ 34,949	$ 44,467