Schedule II - Valuation and Qualifying Accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
ALLOWANCE FOR DOUBTFUL ACCOUNTS
Balance at beginning of year	$ 12,946	$ 15,048	$ 17,251
Charged to income	1,415	4,269	2,665
Recoveries and adjustments	(1,262)	(1,744)	(1,100)
Net additions	153	2,525	1,565
Less uncollectible accounts written off	(6,550)	(4,627)	(3,768)
Balance at end of year	6,549	12,946	15,048
Alabama Gas Corporation
ALLOWANCE FOR DOUBTFUL ACCOUNTS
Balance at beginning of year	12,100	14,200	16,400
Charged to income	1,409	4,202	2,655
Recoveries and adjustments	(1,263)	(1,745)	(1,094)
Net additions	146	2,457	1,561
Less uncollectible accounts written off	(6,546)	(4,557)	(3,761)
Balance at end of year	$ 5,700	$ 12,100	$ 14,200