Merger Agreement (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Business Combinations [Abstract]
Merger, Description	Duke Energy and Progress Energy entered into an Agreement and Plan of Merger (the Merger Agreement). Pursuant to the Merger Agreement, Progress Energy will be acquired by Duke Energy in a stock-for-stock transaction (the Merger) and become a wholly owned subsidiary of Duke Energy.
Merger share exchange ratio	2.6125
Merger Share Exchange Ratio, Adjusted	0.87083
Settlement Agreement, Date	September 2, 2011
Settlement Agreement, Description	Under the settlement agreement with the North Carolina Public Staff, Progress Energy and Duke Energy will provide $650 million in system fuel cost savings for customers in North Carolina and South Carolina over the five years following the close of the Merger, maintain their current level of community support in North Carolina for the next four years, and provide $15 million for low-income energy assistance and workforce development in North Carolina. The settlement agreement also provides that direct merger-related expenses will not be recovered from customers; however, PEC may request recovery of costs incurred to create operational savings.
Settlement Agreement, Fuel Savings	$ 650
Loss Contingencies [Line Items]
Settlement Agreement, Low Income And Workforce Assistance	15
Exit cost liability recognized	5
Estimated exit cost liability	17
Merger and integration costs, net of tax	46
Employee Rentention Member
Loss Contingencies [Line Items]
Loss Contingency Unrecorded Estimate Of Possible Loss	14
Special Termination Benefits [Member]
Loss Contingencies [Line Items]
Loss Contingency Unrecorded Estimate Of Possible Loss Range Low	90
Loss Contingency Unrecorded Estimate Of Possible Loss Range High	100
Number of accepted VSP requests	650
Transmission Construction Commitments Member
Loss Contingencies [Line Items]
Loss Contingency Unrecorded Estimate Of Possible Loss Range Low	75
Loss Contingency Unrecorded Estimate Of Possible Loss Range High	$ 150