Note 6 - Employee Benefit Plans (Details) - Employee Benefit Plans (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Long-term asset	$ 117		$ 33
Defined Benefit Plan Change In Benefit Obligation [Member] | Long Term Asset [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Long-term asset	117		33
Defined Benefit Plan Change In Benefit Obligation [Member] | Current Liability [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Current liability	(2)		(2)
Defined Benefit Plan Change In Benefit Obligation [Member] | Current Liability [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Current liability			(12)
Defined Benefit Plan Change In Benefit Obligation [Member] | Long Term Liability [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Long-term liability	(168)		(240)
Total liability at December 31,	(53)		(209)
Defined Benefit Plan Change In Benefit Obligation [Member] | Long Term Liability [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Long-term liability	(233)		(265)
Total liability at December 31,	(233)		(277)
Defined Benefit Plan Change In Benefit Obligation [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefits paid	(65)		(59)
Benefit obligation, January 1,	1,046		968
Service cost	29		28
Interest cost	43		44
Actuarial loss (gain)	(93)		66
Plan curtailment and settlements			(1)
Benefit obligation, December 31,	960		1,046
Funded status at end of year	(53)		(209)
Defined Benefit Plan Change In Benefit Obligation [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Employee contributions	3		1
Benefits paid	(23)		(19)
Benefit obligation, January 1,	354		397
Service cost	3		4
Interest cost	14		17
Actuarial loss (gain)	(26)		(22)
Plan amendments			(25)
Medicare Part D reimbursements	1		1
Benefit obligation, December 31,	326		354
Funded status at end of year	(233)		(277)
Defined Benefit Plan Change In Fair Value Of Plan Assets [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, January 1,	837		754
Actual return on plan assets	134		101
Employer contributions	1		42
Benefits paid	(65)		(59)
Plan curtailment and settlements			(1)
Fair value of plan assets, December 31,	907		837
Defined Benefit Plan Change In Fair Value Of Plan Assets [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, January 1,	77		67
Actual return on plan assets	16		10
Employee contributions	3		1
Employer contributions	19		17
Benefits paid	(23)		(19)
Medicare Part D reimbursements	1		1
Fair value of plan assets, December 31,	93		77
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, January 1,	845	[1]
Employer contributions			40
Service cost	29		28		14
Interest cost	43		44		29
Fair value of plan assets, December 31,	916	[1]	845	[1]
Accumulated benefit obligation (1)	902	[2]	983	[2]
Discount rate	5.00%		4.20%
Rate of compensation increase	3.70%		3.70%
Pension band increase (2)	2.00%	[3]	2.00%	[3]
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, January 1,	69
Service cost	3		4		1
Interest cost	14		16		6
Fair value of plan assets, December 31,	84		69
Accumulated benefit obligation (1)		[2]		[2]
Discount rate	4.70%		4.00%
Rate of compensation increase	3.70%		3.70%
Pension band increase (2)		[3]		[3]

[1] Includes $9 million at December 31, 2013 and $8 million at December 31, 2012 of medical benefit (health and welfare) component for 401h accounts to fund a portion of the other retirement benefits.

[2] APBO differs from the projected benefit obligation in that the APBO excludes the effect of salary and wage increases.

[3] Only applicable to the Nicor Gas union employees.