Schedule II - Valuation and Qualifying Accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
ALLOWANCE FOR DOUBTFUL ACCOUNTS
Balance at beginning of year	$ 15,048	$ 17,251	$ 12,868
Charged to income	4,269	2,665	11,200
Recoveries and adjustments	(1,744)	(1,100)	(512)
Net additions	2,525	1,565	10,688
Less uncollectible accounts written off	(4,627)	(3,768)	(6,305)
Balance at end of year	12,946	15,048	17,251
Alabama Gas Corporation
ALLOWANCE FOR DOUBTFUL ACCOUNTS
Balance at beginning of year	14,200	16,400	12,100
Charged to income	4,202	2,655	11,122
Recoveries and adjustments	(1,745)	(1,094)	(517)
Net additions	2,457	1,561	10,605
Less uncollectible accounts written off	(4,557)	(3,761)	(6,305)
Balance at end of year	$ 12,100	$ 14,200	$ 16,400