Note 2 - Significant Accounting Policies and Methods of Application (Detail) - Potentially Dilutive Common Share Calculation (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Net income (loss) attributable to AGL Resources Inc. (in Dollars)	$ 9		$ (3)		$ 173		$ 139
Basic weighted average number of shares outstanding (1)	117.1	[1]	78.1	[1]	116.9	[1]	77.9	[1]
Effect of dilutive securities	0.4		0		0.4		0.5
Diluted weighted average number of shares outstanding	117.5		78.1		117.3		78.4
Basic (in Dollars per share)	$ 0.08		$ (0.04)		$ 1.48		$ 1.79
Diluted (in Dollars per share)	$ 0.08		$ (0.04)		$ 1.48		$ 1.78

[1] Daily weighted average shares outstanding.