Condensed Consolidated Statementa of Other Comprehensive Income (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Net income	$ 164		$ 139
Retirement benefit plans
Reclassification of actuarial losses to net benefit cost (net of income tax of $2 and $1)	4		1
Reclassification of prior service credits to net benefit cost	(1)
Retirement benefit plans	3		1
Cash flow hedges, net of tax
Net derivative instrument gains (losses) arising during the period (net of income tax of $1 and $1)	2	[1]	(2)
Reclassification of realized derivative instrument losses to net income (net of income tax of $1)	2	[1]
Cash flow hedges, net	4	[1]	(2)
Other comprehensive income (loss), net of tax	7	[1]	(1)
Comprehensive income	171		138
Less comprehensive income attributable to noncontrolling interest	10		9
Comprehensive income attributable to AGL Resources Inc.	$ 161		$ 129

[1] All amounts are net of income taxes. Amounts in parentheses indicate debits to Accumulated Other Comprehensive Loss.