Acquisition (Details) (USD $)	3 Months Ended
	Mar. 31, 2014 MW		Dec. 31, 2013 MW
Business Acquisition [Line Items]
Number of power plants to be disposed of	6
Ownership percentage before divestiture of business	100.00%
Proceeds from Sale of Productive Assets	$ 1,570,000,000
Power generation capacity	9,849		9,427
Number of 525 MW generation blocks to be acquired in the Guadalupe acquisition	2
Guadalupe Energy Center [Member]
Business Acquisition [Line Items]
Power generation capacity	1,050
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	625,000,000
Guadalupe Expansion Capacity [Member]
Business Acquisition [Line Items]
Power generation capacity	400
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	15,000,000
Incremental CCFC Term Loans [Member]
Business Acquisition [Line Items]
Debt Instrument, Face Amount	425,000,000
Oneta Energy Center [Member]
Business Acquisition [Line Items]
Power generation capacity	1,134
Carville Energy Center [Member]
Business Acquisition [Line Items]
Power generation capacity	501	[1]
Decatur Energy Center [Member]
Business Acquisition [Line Items]
Power generation capacity	795
Hog Bayou Energy Center [Member]
Business Acquisition [Line Items]
Power generation capacity	237
Santa Rosa Energy Center [Member]
Business Acquisition [Line Items]
Power generation capacity	225
Columbia Energy Center [Member]
Business Acquisition [Line Items]
Power generation capacity	606	[1]
Six Power Plants [Member]
Business Acquisition [Line Items]
Power generation capacity	3,498
Minimum [Member]
Business Acquisition [Line Items]
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property	725,000,000
Maximum [Member]
Business Acquisition [Line Items]
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property	$ 775,000,000

[1] Indicates combined-cycle cogeneration power plant.