Property, Plant and Equipment (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended														3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2011 weeks	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 PEC	Dec. 31, 2010 PEC	Dec. 31, 2009 PEC	Dec. 31, 2011 PEC Mayo	Dec. 31, 2010 PEC Mayo	Dec. 31, 2011 PEC Harris	Dec. 31, 2010 PEC Harris	Dec. 31, 2011 PEC Brunswick	Dec. 31, 2010 PEC Brunswick	Dec. 31, 2011 PEC Roxboro Unit 4	Dec. 31, 2010 PEC Roxboro Unit 4	Mar. 31, 2010 PEF	Dec. 31, 2010 PEF	Dec. 31, 2011 PEF	Dec. 31, 2009 PEF	Dec. 31, 2011 PEF Crystal River Unit 3	Dec. 31, 2010 PEF Crystal River Unit 3	Dec. 31, 2011 PEF Intercession City Unit P11	Dec. 31, 2010 PEF Intercession City Unit P11
Utility Plant
Production plant	$ 16,728	$ 16,042
Transmission plant	3,853	3,530
Distribution plant	9,053	8,715
General plant and other	1,431	1,421
Utility plant in service	31,065	29,708		17,439	16,388											13,155	13,461
Production plant depreciable lives	3-41
Transmission plant depreciable lives	7-75
Distribution plant depreciable lives	13-67
General plant and other depreciable lives	5-35
Net carrying value of facilities intended to retire				163
Net carrying value of facilities retired				15
Composite AFUDC rate				8.70%	9.20%	9.20%									8.80%	7.40%	7.40%	8.80%
Depreciation provisions, percentage	2.30%	2.00%	2.40%
Depreciation provisions, amount	675	635	626
Nuclear fuel, net of amortization	767	674		540	480											194	227
Nuclear fuel, not yet in service	575	367
Nuclear fuel, amortization expense	160	132	159
Accelerated recovery of construction work in progress																519	555
Component of nuclear cost-recovery clause regulatory asset																237	177
Joint Ownership of Generating Facilities
Company ownership interest							83.83%	83.83%	83.83%	83.83%	81.67%	81.67%	87.06%	87.06%					91.78%	91.78%	66.67%	66.67%
Plant investment							807	798	3,254	3,255	1,739	1,702	733	706					909	901	23	23
Accumulated depreciation							296	294	1,635	1,604	951	939	470	457					498	497	12	11
Construction work in progress							13	8	66	16	52	38	12	22					803	648	0	0
Asset Retirement Obligations
Asset retirement costs included in utility plant related to nuclear decommissioning of irradiated plant, net of accumulated depreciation	87	90
Fair value of nuclear decommissioning trust funds	1,647	1,571		1,088	1,017											554	559
Nuclear decommissioning cost provisions, included in depreciation and amortization expense	31	31	31
Expenses recognized for the disposal or removal of utility assets that do not meet the definition of AROs	(98)	87	141
Removal costs	1,302	1,503
Nonirradiated decommissioning costs	223	233
Dismantlement costs	125	121
Non-ARO cost of removal	1,650	1,857
Asbestos abatement costs				23	26											27	29
Landfill capping costs				6	3											6	7
Asset retirement obligation roll forward
Asset retirement obligations, beginning balance	1,200	1,170
Additions	0	4
Accretion expense	67	65
Revisions to prior estimates	(2)	(39)
Asset retirement obligations, ending balance	1,265	1,200	1,170
Insurance
NEIL primary coverage per company at each nuclear plant	500
NEIL decontamination, premature decommissioning and excess property insurance limits on each nuclear plant	1,750
Initial weeks of insurance coverage	52
Insurance coverage amount per week range, bottom of range	3.5
Insurance coverage amount per week range, top of range	4.5
Additional weeks of insurance coverage, bottom of range	71
Additional weeks of insurance coverage, top of range	110
Percentage cost of original insurance coverage additional weeks are provided	80.00%
NEIL primary coverage, subject to retrospective premium assessments of up to	29
NEIL decontamination, decommissioning and excess property coverage, subject to retrospective premium assessments of up to	40
NEIL incremental replacement power costs coverage, subject to retrospective premium assessments of up to	25
Insured public liability limit per nuclear incident	12,595
Pro rata assessment for each reactor owned for each incident exceeding public liability insurance	117.5
Annual payment limit to pro rata assessments	17.5
Industry aggregate limit	3,240
All-risk property insurance program limit per loss	600
All-risk property insurance program basic deductible per loss	$ 2.5