Discontinued Operations Narrative (Details) (USD $)	3 Months Ended					1 Months Ended		1 Months Ended
	Mar. 31, 2014 North Louisiana and East Texas Natural Gas and Oil Properties	Dec. 31, 2013 North Louisiana and East Texas Natural Gas and Oil Properties	Sep. 30, 2013 North Louisiana and East Texas Natural Gas and Oil Properties	Dec. 31, 2013 North Louisiana and East Texas Natural Gas and Oil Properties Natural Gas Bcf	Dec. 31, 2013 North Louisiana and East Texas Natural Gas and Oil Properties Oil MBbls	Oct. 31, 2013 Black Warrior Basin Properties Alabama	Dec. 31, 2012 Black Warrior Basin Properties Alabama Natural Gas Mcf	Apr. 30, 2014 Alabama Gas Corporation
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Expected amount of consideration to be received								$ 1,600,000,000
Expected proceeds from sale of Alagasco								1,280,000,000
Expected amount of debt to be assigned								320,000,000
Sale price of gas and oil properties	30,300,000
Impairment of oil and gas properties held-for-sale	1,700,000	5,200,000	24,600,000
Proved Developed Reserves (Volume)				23,000,000	91		97,000,000
Proceeds from the sale of oil and gas property						160,000,000
Gain on disposition of oil and gas property						$ 35,000,000