Condensed Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net income (loss)	$ 9	$ (4)	$ 183	$ 149
Retirement benefit plans
Reclassification of losses and prior service costs to net benefit cost (net of income tax of $2 and $6 for the three and nine months ended September 30, 2012)	2	0	10	0
Retirement benefit plans	2	0	10	0
Cash flow hedges, net of tax
Net derivative instrument losses (gains) arising during the period (net of income tax of $1 and $2 for the three and nine months ended September 30, 2012)	2	0	4	(1)
Cash flow hedges, net	2	0	4	(1)
Other comprehensive income (loss), net of tax	4	0	14	(1)
Comprehensive income (loss)	13	(4)	197	148
Less comprehensive income (loss) attributable to noncontrolling interest	0	(1)	10	10
Comprehensive income (loss) attributable to AGL Resources Inc.	$ 13	$ (3)	$ 187	$ 138