Acquisitions and Sales of Other Assets (Purchase Price Calculation) (Details) (USD $) In Millions, except Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Jul. 02, 2012	Dec. 31, 2011
Significant Acquisitions and Disposals [Line Items]
Progress Energy common shares outstanding	706,000,000	704,000,000	704,000,000		445,000,000
Exchange ratio				87.083%
Fair value of outstanding earned stock compensation awards				$ 62
Total estimated purchase price	$ 18,071			$ 18,071
Progress Energy [Member]
Significant Acquisitions and Disposals [Line Items]
Progress Energy common shares outstanding	100	100