CONSOLIDATED STATEMENTS OF INCOME (LOSS) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Statement [Abstract]
Revenues	$ 2,338	$ 2,373	$ 2,317
Operating expenses
Cost of gas	1,097	1,164	1,142
Operation and maintenance	490	497	497
Depreciation and amortization	186	160	158
Business Combination Integration Related Costs	68	6	0
Taxes other than income taxes	57	46	44
Total operating expenses	1,898	1,873	1,841
Operating income	440	500	476
Other income (expense)	7	(1)	9
Interest expense, net	(136)	(109)	(101)
Total other expense	(129)	(110)	(92)
(Loss) earnings before Income Taxes	311	390	384
Income tax (benefit) expense	125	140	135
Net (loss) income	186	250	249
Less net (loss) income attributable to the noncontrolling interest (Note 8)	14	16	27
Net (loss) income attributable to AGL Resources Inc	$ 172	$ 234	$ 222
Per common share data (Note 2)
Basic (loss) earnings per common share attributable to AGL Resources Inc. common shareholders	$ 2.14	$ 3.02	$ 2.89
Diluted (loss) earnings per common share attributable to AGL Resources Inc. common shareholders	$ 2.12	$ 3.00	$ 2.88
Cash dividends declared per common share	$ 1.90	$ 1.76	$ 1.72
Weighted-average number of common shares outstanding (Note 2)
Basic	80.4	77.4	76.8
Diluted	80.9	77.8	77.1