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				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Net income attributable to AGL Resources Inc. (in Dollars)	$ 34		$ 18		$ 164		$ 142
Basic weighted average number of shares outstanding (1)	116.9	[1]	77.9	[1]	116.8	[1]	77.8	[1]
Effect of dilutive securities	0.3		0.6		0.3		0.5
Diluted weighted average number of shares outstanding	117.2		78.5		117.1		78.3
Basic (in Dollars per share)	$ 0.28		$ 0.23		$ 1.40		$ 1.83
Diluted (in Dollars per share)	$ 0.28		$ 0.23		$ 1.40		$ 1.82

[1] Daily weighted average shares outstanding.