CONSOLIDATED STATEMENTS OF CAPITALIZATION (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2013 First Mortgage Bonds Series Due March 1, 2013	Dec. 31, 2013 First Mortgage Bonds Series Due April 1, 2014	Dec. 31, 2013 First Mortgage Bonds Series Due Sept. 1, 2017	Dec. 31, 2013 First Mortgage Bonds Series Due Aug. 1, 2018	Dec. 31, 2013 First Mortgage Bonds Series Due June 1, 2019	Dec. 31, 2013 First Mortgage Bonds Series Due Nov. 15, 2020	Dec. 31, 2013 First Mortgage Bonds Series Due Sept. 1, 2037	Dec. 31, 2013 First Mortgage Bonds Series Due Aug. 1, 2038	Dec. 31, 2013 First Mortgage Bonds Series Due Aug. 15, 2041	Dec. 31, 2013 Capital Lease Obligations
Schedule of Capitalization, Long-term Debt [Line Items]
Interest rate, stated percentage (in hundredths)	4.875%	5.50%	4.375%	5.80%	5.125%	3.20%	6.25%	6.50%	4.75%
Debt instrument, interest rate, stated percentage rate range, minimum (in hundredths)										11.20%
Debt instrument, interest rate, stated percentage rate range, maximum (in hundredths)										14.30%
Debt instrument, maturity date	Mar. 01, 2013	Apr. 01, 2014	Sep. 01, 2017	Aug. 01, 2018	Jun. 01, 2019	Nov. 15, 2020	Sep. 01, 2037	Aug. 01, 2038	Aug. 15, 2041
Debt instrument, maturity date range, end										Dec. 31, 2060