Condensed Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Net income	$ 139	$ 134
Retirement benefit plans
Reclassification of losses and prior service costs to net periodic pension cost (net of income tax of $1 in 2012)	1	0
Retirement benefit plans, net	1	0
Cash flow hedges, net of tax
Net derivative instrument losses arising during the period (net of income tax of $1 in 2012 and $1 in 2011)	(2)	(1)
Cash flow hedges, net	(2)	(1)
Other comprehensive loss, net of tax	(1)	(1)
Comprehensive income	138	133
Less comprehensive income attributable to noncontrolling interest	0	0
Comprehensive income attributable to AGL Resources Inc.	$ 138	$ 133