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												12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Potentially Dilutive Common Share Calculation [Abstract]
Net income attributable to AGL Resources Inc. (in Dollars)	$ 82	$ 28	$ 49	$ 154	$ 98	$ 9	$ 34	$ 130	$ 33	$ (3)	$ 18	$ 124	$ 313		$ 271		$ 172
Basic weighted average number of shares outstanding (1)													117.9	[1]	117.0	[1]	80.4	[1]
Effect of dilutive securities													0.4		0.5		0.5
Diluted weighted average number of shares outstanding (2)													118.3	[2]	117.5	[2]	80.9	[2]
Earnings per share
Basic (in Dollars per share)	$ 0.69	$ 0.24	$ 0.41	$ 1.31	$ 0.84	$ 0.08	$ 0.28	$ 1.12	$ 0.37	$ (0.04)	$ 0.23	$ 1.60	$ 2.65		$ 2.32		$ 2.14
Diluted (2) (in Dollars per share)	$ 0.68	$ 0.24	$ 0.41	$ 1.31	$ 0.84	$ 0.08	$ 0.28	$ 1.11	$ 0.37	$ (0.04)	$ 0.23	$ 1.59	$ 2.64	[2]	$ 2.31	[2]	$ 2.12	[2]

[1] Daily weighted average shares outstanding.

[2] There were no outstanding stock options excluded from the computation of diluted earnings per common share attributable to AGL Resources Inc. for any of the periods presented because their effect would have been anti-dilutive, as the exercise prices were greater than the average market price.