Note 13 - Revision to Prior Period Financial Statements (Details) - Revisions to Condensed Consolidated Statements of Income (USD $)	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Operating revenues	$ 2,462,000,000	[1]	$ 1,612,000,000	[1]
Operating expenses
Cost of goods sold	1,400,000,000	[1]	920,000,000	[1]
Operation and maintenance	289,000,000	[1]	231,000,000	[1]
Depreciation and amortization	93,000,000	[1]	102,000,000	[1]
Taxes other than income taxes	88,000,000	[1]	69,000,000	[1]
Total operating expenses	1,870,000,000	[1]	1,322,000,000	[1]
Operating income	592,000,000	[1]	290,000,000	[1]
Other income	3,000,000	[1]	5,000,000	[1]
Interest expense, net	(46,000,000)		(45,000,000)
Income before income taxes	549,000,000		250,000,000
Income tax expense	203,000,000		91,000,000
Income from continuing operations	346,000,000		159,000,000
(Loss) income from discontinued operations	(50,000,000)	[2],[3]	1,000,000	[2],[3]
Net income	296,000,000		160,000,000
Less net income attributable to the noncontrolling interest	12,000,000		10,000,000
Net income attributable to AGL Resources Inc.	284,000,000	[2]	150,000,000	[2]
Basic earnings (loss) per common share (2)
Continuing operations (in Dollars per share)	$ 2.82	[2],[4]	$ 1.27	[2],[4]
Discontinued operations (in Dollars per share)	$ (0.43)	[2],[4]	$ 0.01	[2],[4]
Basic earnings per common share attributable to AGL Resources Inc. common shareholders (in Dollars per share)	$ 2.39	[2]	$ 1.28	[2]
Diluted earnings (loss) per common share (2)
Continuing operations (in Dollars per share)	$ 2.81	[2],[4]	$ 1.26	[2],[4]
Discontinued operations (in Dollars per share)	$ (0.43)	[2],[4]	$ 0.01	[2],[4]
Diluted earnings per common share attributable to AGL Resources Inc. common shareholders (in Dollars per share)	$ 2.38	[2]	$ 1.27	[2]
Scenario, Previously Reported [Member]
Operating revenues	2,474,000,000	[5]	1,622,000,000	[5]
Operating expenses
Cost of goods sold	1,400,000,000	[5]	920,000,000	[5]
Operation and maintenance	289,000,000	[5]	232,000,000	[5]
Depreciation and amortization	93,000,000	[5],[6]	102,000,000	[5],[6]
Taxes other than income taxes	88,000,000	[5]	70,000,000	[5]
Total operating expenses	1,870,000,000	[5]	1,324,000,000	[5]
Operating income	604,000,000	[5]	298,000,000	[5]
Other income	3,000,000	[5]	5,000,000	[5]
Interest expense, net	(48,000,000)	[5]	(46,000,000)	[5]
Income before income taxes	559,000,000	[5]	257,000,000	[5]
Income tax expense	207,000,000	[5]	94,000,000	[5]
Income from continuing operations	352,000,000	[5]	163,000,000	[5]
(Loss) income from discontinued operations	(50,000,000)	[5]	1,000,000	[5]
Net income	302,000,000	[5],[6]	164,000,000	[5],[6]
Less net income attributable to the noncontrolling interest	12,000,000	[5]	10,000,000	[5]
Net income attributable to AGL Resources Inc.	290,000,000	[5]	154,000,000	[5]
Basic earnings (loss) per common share (2)
Continuing operations (in Dollars per share)	$ 2.87	[4],[5]	$ 1.30	[4],[5]
Discontinued operations (in Dollars per share)	$ (0.43)	[4],[5]	$ 0.01	[4],[5]
Basic earnings per common share attributable to AGL Resources Inc. common shareholders (in Dollars per share)	$ 2.44	[5]	$ 1.31	[5]
Diluted earnings (loss) per common share (2)
Continuing operations (in Dollars per share)	$ 2.87	[4],[5]	$ 1.30	[4],[5]
Discontinued operations (in Dollars per share)	$ (0.43)	[4],[5]	$ 0.01	[4],[5]
Diluted earnings per common share attributable to AGL Resources Inc. common shareholders (in Dollars per share)	$ 2.44	[5]	$ 1.31	[5]
Restatement Adjustment [Member]
Operating revenues	(12,000,000)		(10,000,000)
Operating expenses
Operation and maintenance			(1,000,000)
Taxes other than income taxes			(1,000,000)
Total operating expenses			(2,000,000)
Operating income	(12,000,000)		(8,000,000)
Interest expense, net	2,000,000		1,000,000
Income before income taxes	(10,000,000)		(7,000,000)
Income tax expense	(4,000,000)		(3,000,000)
Income from continuing operations	(6,000,000)		(4,000,000)
Net income	(6,000,000)		(4,000,000)
Net income attributable to AGL Resources Inc.	$ (6,000,000)		$ (4,000,000)
Basic earnings (loss) per common share (2)
Continuing operations (in Dollars per share)	$ (0.05)	[4]	$ (0.03)	[4]
Discontinued operations (in Dollars per share)		[4]		[4]
Basic earnings per common share attributable to AGL Resources Inc. common shareholders (in Dollars per share)	$ (0.05)		$ (0.03)
Diluted earnings (loss) per common share (2)
Continuing operations (in Dollars per share)	$ (0.06)	[4]	$ (0.04)	[4]
Discontinued operations (in Dollars per share)		[4]		[4]
Diluted earnings per common share attributable to AGL Resources Inc. common shareholders (in Dollars per share)	$ (0.06)		$ (0.04)

[1] Amounts revised to include prior period adjustments. See Note 13 for additional information.

[2] Amounts revised and or include prior period adjustments. See Note 13 for additional information.

[3] For additional information on our discontinued operations, see Note 12.

[4] Excludes net income attributable to the noncontrolling interest.

[5] Reflects the reclassification of the Tropical Shipping amounts as discontinued operations.

[6] Reflects the reclassification of the Tropical Shipping amounts as held for sale.