Note 6 - Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2012

Schedule of Defined Benefit Plans Disclosures [Table Text Block]

	Pension plans						Other retirement plans
Dollars in millions	2012			2011			2012			2011
Change in plan assets
Fair value of plan assets, January 1,	$	754		$	344		$	67		$	71
Plan assets acquired in Nicor merger		0			388			0			0
Actual return on plan assets		101			(7	)		10			(3	)
Employee contributions		0			0			1			0
Employer contributions		42			58			17			8
Benefits paid		(59	)		(28	)		(19	)		(9	)
Medicare Part D reimbursements		0			0			1			0
Plan curtailment and settlements		(1	)		(1	)		0			0
Fair value of plan assets, December 31,	$	837		$	754		$	77		$	67
Change in benefit obligation
Benefit obligation, January 1,	$	968		$	531		$	397		$	107
Benefit obligations acquired in Nicor merger		0			345			0			273
Service cost		28			14			4			1
Interest cost		44			29			17			6
Actuarial loss (gain)		66			78			(22	)		18
Plan amendments		0			0			(25	)		0
Medicare Part D reimbursements		0			0			1			1
Benefits paid		(59	)		(28	)		(19	)		(9	)
Employee contributions		0			0			1			0
Plan curtailment and settlements		(1	)		(1	)		0			0
Benefit obligation, December 31,	$	1,046		$	968		$	354		$	397
Funded status at end of year	$	(209	)	$	(214	)	$	(277	)	$	(330	)
Amounts recognized in the Consolidated Statements of Financial Position consist of
Long-term asset	$	33		$	26		$	0		$	0
Current liability		(2	)		(2	)		(12	)		(14	)
Long-term liability		(240	)		(238	)		(265	)		(316	)
Total liability at December 31,	$	(209	)	$	(214	)	$	(277	)	$	(330	)
Accumulated benefit obligation (2)	$	983		$	910			n/a			n/a
Supplemental information for underfunded pension plans included above as of December 31, 2012:
Aggregate benefit obligation		n/a		$	604			n/a			n/a
Aggregate accumulated benefit obligation		n/a			570			n/a			n/a
Aggregate fair value of plan assets		n/a			363			n/a			n/a
Assumptions used to determine benefit obligations
Discount rate		4.2	%		4.6	%		4.0	%		4.5	%
Rate of compensation increase		3.7	%		3.7	%		3.7	%		3.7	%
Pension band increase (1)		2.0	%		2.0	%		n/a			n/a

Schedule of Net Benefit Costs [Table Text Block]

	Pension plans									Other retirement plans
Dollars in millions	2012			2011			2010			2012			2011			2010
Service cost	$	28		$	14		$	11		$	4		$	1		$	0
Interest cost		44			29			27			16			6			6
Expected return on plan assets		(64	)		(33	)		(28	)		(5	)		(5	)		(5	)
Net amortization of prior service credit		(2	)		(2	)		(2	)		(3	)		(4	)		(4	)
Recognized actuarial loss		34			14			10			9			2			2
Net periodic benefit cost	$	40		$	22		$	18		$	21		$	0		$	(1	)
Assumptions used to determine benefit costs
Discount rate (1)		4.6	%		5.4	%		6.0	%		4.5	%		5.2	%		5.8	%
Expected return on plan assets (1)		8.4	%		8.5	%		8.8	%		8.5	%		8.2	%		8.8	%
Rate of compensation increase(1)		3.7	%		3.7	%		3.7	%		3.8	%		3.7	%		3.7	%
Pension band increase (1) (2)		2.0	%		2.0	%		n/a			n/a			n/a			n/a

Schedule of Health Care Cost Trend Rates [Table Text Block]

	2012			2011
Health care cost trend rate assumed for next year		8.4	%		8.6	%
Ultimate rate to which the cost trend rate is assumed to decline		4.5	%		4.5	%
Year that reaches ultimate trend rate		2030			2030

Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates [Table Text Block]

Dollars in millions	Effect on service and interest cost			Effect on benefit obligation
1% Health care cost trend rate increase	$	1		$	17
1% Health care cost trend rate decrease		(1	)		(14	)

Schedule of Net Periodic Benefit Cost Not yet Recognized [Table Text Block]

	Net regulatory assets					Accumulated OCI						Total
In millions	Pension plan		Other retirement plans			Pension plan			Other retirement plans			Pension plan			Other retirement plans
December 31, 2012:
Prior service credit	$	0	$	(24	)	$	(11	)	$	(2	)	$	(11	)	$	(26	)
Net loss		146		83			324			52			470			135
Total	$	146	$	59		$	313		$	50		$	459		$	109
December 31, 2011:
Prior service cost (credit)	$	1	$	1		$	(13	)	$	(4	)	$	(12	)	$	(3	)
Net loss		162		119			312			51			474			170
Total	$	163	$	120		$	299		$	47		$	462		$	167

Schedule of Amounts in Accumulated Other Comprehensive Income (Loss) to be Recognized over Next Fiscal Year [Table Text Block]

	Net Regulatory Asset					Accumulated OCI						Total
In millions	Pension plans		Other retirement plans			Pension plans			Other retirement plans			Pension plans			Other retirement plans
Amortization of prior service credit	$	0	$	(3	)	$	(2	)	$	(2	)	$	(2	)	$	(5	)
Amortization of net loss		9		6			24			3			33			8

Schedule of Expected Benefit Payments [Table Text Block]

In millions	Pension plans		Other retirement plans
2013	$	57	$	19
2014		60		20
2015		62		21
2016		65		21
2017		68		22
2018-2022		377		121