Condensed Consolidated Statements of Other Comprehensive Income (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Net income	$ 50	$ 35	$ 214	$ 174
Retirement benefit plans
Reclassification of actuarial losses to net benefit cost (net of income tax of $3 and $5 for the three and six months ended June 30, 2013, and $3 and $4 for the three and six months ended June 30, 2012)	4	7	8	8
Reclassification of prior service credits to net benefit cost (net of income tax of $1 for the six months ended June 30, 2013)			(1)
Retirement benefit plans	4	7	7	8
Cash flow hedges, net of tax
Net derivative instrument gains (losses) arising during the period (net of income tax of $1 for the three months ended June 30, 2013, and $3 and $1 for the three and six months ended June 30, 2012)	(1)	4	1	2
Reclassification of realized derivative instrument (gains) losses to net income (net of income tax of $1 for the six months ended June 30, 2013)	(1)		1
Cash flow hedges, net	(2)	4	2	2
Other comprehensive income, net of tax	2	11	9	10
Comprehensive income	52	46	223	184
Less comprehensive income attributable to noncontrolling interest	1	1	11	10
Comprehensive income attributable to AGL Resources Inc.	$ 51	$ 45	$ 212	$ 174