v2.4.0.8
Summary of Significant Accounting Policies (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2013
Freestone Energy Center [Member]
Dec. 31, 2013
Hidalgo Energy Center [Member]
Dec. 31, 2013
Debt Service
Dec. 31, 2012
Debt Service
Dec. 31, 2013
Rent Reserve [Member]
Dec. 31, 2012
Rent Reserve [Member]
Dec. 31, 2013
Construction Major Maintenance
Dec. 31, 2012
Construction Major Maintenance
Dec. 31, 2013
Security Project Insurance
Dec. 31, 2012
Security Project Insurance
Dec. 31, 2013
Other
Dec. 31, 2012
Other
Dec. 31, 2013
Greenfield [Member]
Dec. 31, 2013
Whitby [Member]
Dec. 31, 2012
Comprehensive Income [Member]
Dec. 31, 2011
Comprehensive Income [Member]
Dec. 31, 2012
Cash Flow Statement [Member]
Dec. 31, 2011
Cash Flow Statement [Member]
Restricted Cash and Cash Equivalents Items [Line Items]                                        
Prior Period Reclassification Adjustment                                 $ (6) $ (14) $ 5 $ 0
Held-to-maturity Securities, Restricted 24 25                                    
Current 203 193     11 [1] 11 [1] 3 0 35 32 151 101 3 49            
Non-current 69 60     41 [1] 41 [1] 0 0 20 14 6 3 2 2            
Total 272 253     52 [1] 52 [1] 3 0 55 46 157 104 5 51            
Prior Period Adjustment [Abstract]                                        
Ownership percentage in equity method investment                             50.00% 50.00%        
Cash and cash equivalents subject to project finance facilities and lease agreements 292 131                                    
Inventory 364 301                                    
Property, plant and equipment, salvage value (as a percent) 10.00%                                      
Property, plant and equipment, salvage value of rotables (as a percent) 0.15%                                      
Asset retirement obligations 44 38                                    
Jointly Owned Plants [Abstract]                                        
Jointly Owned Utility Plant, Proportionate Ownership Share     75.00% 78.50%                                
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service     393 255                                
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation     (135) (93)                                
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress     $ 0 $ 0                                
[1] At December 31, 2013 and 2012, amounts restricted for debt service included approximately $24 million and $25 million, respectively, of repurchase agreements with a financial institution containing maturity dates greater than one year.