Merger Agreement (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Business Combinations [Abstract]
Business Acquisition, Date Of Acquisition Agreement	January 8, 2011
Merger, Description	Duke Energy Corporation (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 and become a wholly owned subsidiary of Duke Energy. The Merger Agreement originally had a termination date of January 8, 2012, which has been extended to July 8, 2012. The Merger Agreement can be extended past July 8, 2012, only by mutual agreement of Progress Energy and Duke Energy.
Merger share exchange ratio	2.6125
Merger Share Exchange Ratio, Adjusted	0.87083
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	3
Estimated exit cost liability	17
Merger and integration costs, net of tax	5	14
Merger Dividend Restriction	$ 0.62
Merger Termination Fee, Aquirer	675
Merger Termination Fee, Aquiree	400
Merger Cost Indemnification	30
Property, Plant and Equipment, Additions, Proposed, Settlement	110
Exit cost liability	8
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