Stock-Based Compensation (Weighted-Average Assumptions Used For Option Pricing) (Details)	12 Months Ended
	Dec. 31, 2011 years
Stock-Based Compensation [Abstract]
Risk-free interest rate	2.50%	[1]
Expected dividend yield	5.70%	[2]
Expected life, years	6.0	[3]
Expected volatility	18.80%	[4]
Historical volatility rate	50.00%
Implied volatility rate	50.00%

[1] The risk free rate is based upon the U.S. Treasury Constant Maturity rates as of the grant date.

[2] The expected dividend yield is based upon annualized dividends and the 1-year average closing stock price.

[3] The expected life of options is derived from the simplified method approach.

[4] Volatility is based upon 50% historical and 50% implied volatility. Historic volatility is based on Duke Energy's historical volatility over the expected life using daily stock prices. Implied volatility is the average for all option contracts with a term greater than six months using the strike price closest to the stock price on the valuation date.