Note 2 - Significant Accounting Policies and Methods of Application (Details) - Potentially Dilutive Common Share Calculation (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Potentially Dilutive Common Share Calculation [Abstract]
Net income attributable to AGL Resources Inc. (in Dollars)	$ 28		$ 9		$ 231		$ 173
Basic weighted average number of shares outstanding (1)	118.2	[1]	117.1	[1]	117.8	[1]	116.9	[1]
Effect of dilutive securities	0.3		0.4		0.3		0.4
Diluted weighted average number of shares outstanding	118.5		117.5		118.1		117.3
Basic (in Dollars per share)	$ 0.24		$ 0.08		$ 1.96		$ 1.48
Diluted (in Dollars per share)	$ 0.24		$ 0.08		$ 1.96		$ 1.48

[1] Daily weighted average shares outstanding.