v3.3.0.814
Segment Information (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2015
Sep. 30, 2014
Sep. 30, 2015
Sep. 30, 2014
Revenues from External Customers and Long-Lived Assets [Line Items]        
Operating revenues $ 1,948 $ 2,187 $ 5,036 $ 6,091
Commodity Margin 974 944 [1] 2,166 2,221 [1]
Add: Mark-to-market commodity activity, net and other (99) [1] (25) [2] 21 [3] 111 [3]
Plant operating expense 200 215 732 754
Depreciation and amortization expense 166 153 484 453
Sales, general and other administrative expense 33 37 100 108
Other operating expenses 16 23 56 66
Impairment losses 0 123 0 123
(Gain) on sale of assets, net 0 (753) 0 (753)
(Income) loss from unconsolidated investments in power plants (6) (5) (18) (18)
Income from operations 466 1,126 833 1,599
Interest expense, net of interest income 158 154 468 486
Debt extinguishment costs and other (income) expense, net 1 344 40 361
Income before income taxes 307 628 325 752
Lease levelization 41 49 (1) (7)
Amortization of Intangible Assets 4 4 11 11
West [Member]        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Operating revenues 737 715 1,675 1,696
Commodity Margin 385 361 [1] 843 791 [1]
Add: Mark-to-market commodity activity, net and other 68 [1] 41 [2] 173 [3] 91 [3]
Plant operating expense 87 91 313 291
Depreciation and amortization expense 61 65 193 183
Sales, general and other administrative expense 7 11 23 28
Other operating expenses 8 12 28 39
Impairment losses   0   0
(Gain) on sale of assets, net   0   0
(Income) loss from unconsolidated investments in power plants 0 0 0 0
Income from operations 290 223 459 341
Texas [Member]        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Operating revenues 713 989 1,872 2,611
Commodity Margin 264 346 [1] 583 644 [1]
Add: Mark-to-market commodity activity, net and other (98) [1] (64) [2] (47) [3] 74 [3]
Plant operating expense 62 77 233 250
Depreciation and amortization expense 58 51 157 141
Sales, general and other administrative expense 15 18 47 48
Other operating expenses 2 1 6 4
Impairment losses   0   0
(Gain) on sale of assets, net   0   0
(Income) loss from unconsolidated investments in power plants 0 0 0 0
Income from operations 29 135 93 275
East [Member]        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Operating revenues 506 490 1,511 1,853
Commodity Margin 325 237 [1] 740 786 [1]
Add: Mark-to-market commodity activity, net and other (62) [1] 4 [2] (84) [3] (31) [3]
Plant operating expense 57 55 206 237
Depreciation and amortization expense 48 38 135 129
Sales, general and other administrative expense 10 8 29 32
Other operating expenses 8 6 24 22
Impairment losses   123   123
(Gain) on sale of assets, net   (753)   (753)
(Income) loss from unconsolidated investments in power plants (6) (5) (18) (18)
Income from operations 146 769 280 983
Consolidation, Eliminations [Member]        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Operating revenues (8) (7) (22) (69)
Commodity Margin 0 0 [1] 0 0 [1]
Add: Mark-to-market commodity activity, net and other (7) [1] (6) [2] (21) [3] (23) [3]
Plant operating expense (6) (8) (20) (24)
Depreciation and amortization expense (1) (1) (1) 0
Sales, general and other administrative expense 1 0 1 0
Other operating expenses (2) 4 (2) 1
Impairment losses   0   0
(Gain) on sale of assets, net   0   0
(Income) loss from unconsolidated investments in power plants 0 0 0 0
Income from operations 1 (1) 1 0
Six Power Plants [Member]        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Commodity Margin [2]       81
Operating Segments [Member]        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Operating revenues 1,948 2,187 5,036 6,091
Operating Segments [Member] | West [Member]        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Operating revenues 736 714 1,672 1,692
Operating Segments [Member] | Texas [Member]        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Operating revenues 709 985 1,860 2,592
Operating Segments [Member] | East [Member]        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Operating revenues 503 488 1,504 1,807
Operating Segments [Member] | Consolidation, Eliminations [Member]        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Operating revenues 0 0 0 0
Intersegment Eliminations [Member]        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Operating revenues 0 0 0 0
Intersegment Eliminations [Member] | West [Member]        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Operating revenues 1 1 3 4
Intersegment Eliminations [Member] | Texas [Member]        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Operating revenues 4 4 12 19
Intersegment Eliminations [Member] | East [Member]        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Operating revenues 3 2 7 46
Intersegment Eliminations [Member] | Consolidation, Eliminations [Member]        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Operating revenues $ (8) $ (7) $ (22) $ (69)
Six Power Plants [Member]        
Revenues from External Customers and Long-Lived Assets [Line Items]        
Number of power plants disposed       6
[1] Commodity Margin related to the six power plants sold in our East segment on July 3, 2014, was not significant for the three months ended September 30, 2014. The Commodity Margin related to those power plants was $81 million for the nine months ended September 30, 2014
[2] Includes $41 million and $49 million of lease levelization and $4 million and $4 million of amortization expense for the three months ended September 30, 2015 and 2014
[3] Includes $(1) million and $(7) million of lease levelization and $11 million and $11 million of amortization expense for the nine months ended September 30, 2015 and 2014, respectively.