Long-Term Debt and Notes Payable (Textual) (Details) (USD $)	12 Months Ended								12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Senior Term Loans Swap Level 2	Dec. 31, 2012 Senior Term Loans Swap Level 2	Dec. 31, 2013 Senior Term Loans Senior Term Loans, (floating rate interest LIBOR plus 1.625%; 1.792% at December 31, 2013), due March 31, 2014 to December 17, 2017	Nov. 30, 2011 Senior Term Loans Senior Term Loans, (floating rate interest LIBOR plus 1.375%)	Dec. 31, 2013 Senior Term Loans Senior Term Loans, (floating rate interest LIBOR plus 1.375%) Swap	Dec. 31, 2013 Alabama Gas Corporation	Dec. 31, 2012 Alabama Gas Corporation	Dec. 31, 2011 Alabama Gas Corporation
Debt Instrument [Line Items]
Long-term debt						$ 600,000,000	$ 300,000,000	$ 200,000,000
Interest rate								2.6675%
Interest rate swap liability, fair value				1,800,000	3,300,000
Cross default provision, minimum threshold amount	10,000,000								10,000,000
Interest expense	69,200,000	65,542,000	44,822,000						15,649,000	16,284,000	14,740,000
Interest expense, capitalized	$ 200,000	$ 500,000