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Segment Information - Electric and Gas Revenue by Customer Class (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2022
Jun. 30, 2021
Jun. 30, 2022
Jun. 30, 2021
Revenue, Major Customer [Line Items]        
Revenues $ 4,239 $ 4,020 $ 9,566 $ 8,652
Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenues 4,239 4,020 9,566 8,652
Revenue from Related Parties 0 5 6 12
Commonwealth Edison Co [Member]        
Revenue, Major Customer [Line Items]        
Revenues 1,425 1,517 3,158 3,052
Revenue from Related Parties 3 5 8 11
Commonwealth Edison Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 1,381 1,499 3,068 2,972
Commonwealth Edison Co [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues 44 18 90 80
PECO Energy Co [Member]        
Revenue, Major Customer [Line Items]        
Revenues 816 693 1,863 1,582
Revenue from Related Parties 1 2 2 4
PECO Energy Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 812 686 1,849 1,565
PECO Energy Co [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues 4 7 14 17
Baltimore Gas and Electric Company [Member]        
Revenue, Major Customer [Line Items]        
Revenues 786 682 1,940 1,656
Revenue from Related Parties 3 7 10 13
Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 800 688 1,961 1,644
Baltimore Gas and Electric Company [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues (14) (6) (21) 12
Pepco Holdings LLC [Member]        
Revenue, Major Customer [Line Items]        
Revenues 1,221 1,140 2,626 2,384
Revenue from Related Parties 2 4 6 7
Pepco Holdings LLC [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 1,236 1,098 2,646 2,296
Pepco Holdings LLC [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues (15) 42 (20) 88
Potomac Electric Power Company [Member]        
Revenue, Major Customer [Line Items]        
Revenues 581 523 1,195 1,076
Revenue from Related Parties 2 1 2 3
Potomac Electric Power Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 581 503 1,201 1,030
Potomac Electric Power Company [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues 0 20 (6) 46
Delmarva Power and Light Company [Member]        
Revenue, Major Customer [Line Items]        
Revenues 332 298 763 680
Revenue from Related Parties 2 2 3 4
Delmarva Power and Light Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 333 288 765 661
Delmarva Power and Light Company [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues (1) 10 (2) 19
Atlantic City Electric Company [Member]        
Revenue, Major Customer [Line Items]        
Revenues 309 319 658 629
Revenue from Related Parties 1 1 2 1
Atlantic City Electric Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 324 307 670 606
Atlantic City Electric Company [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues (15) 12 (12) 23
Rate-regulated electric revenues [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 3,934 3,739 8,415 7,609
Rate-regulated electric revenues [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 3,938 3,789 8,460 7,780
Rate-regulated electric revenues [Member] | Commonwealth Edison Co [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1,387 1,503 3,075 2,977
Rate-regulated electric revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1,381 1,499 3,068 2,972
Revenue from Related Parties 3 5 8 11
Rate-regulated electric revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 9 9 15 16
Rate-regulated electric revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 819 759 1,675 1,502
Rate-regulated electric revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 312 377 736 744
Rate-regulated electric revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 11 138 165 271
Rate-regulated electric revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 5 11 20 22
Rate-regulated electric revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 234 214 472 433
Rate-regulated electric revenues [Member] | PECO Energy Co [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 707 602 1,441 1,251
Rate-regulated electric revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 704 603 1,436 1,254
Revenue from Related Parties 1 1 2 3
Rate-regulated electric revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 4 0 7 0
Rate-regulated electric revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 431 383 918 816
Rate-regulated electric revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 126 99 237 199
Rate-regulated electric revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 72 59 136 116
Rate-regulated electric revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 7 8 15 17
Rate-regulated electric revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 68 54 130 106
Rate-regulated electric revenues [Member] | Baltimore Gas and Electric Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 642 560 1,377 1,180
Rate-regulated electric revenues [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 639 561 1,373 1,182
Revenue from Related Parties 2 4 3 5
Rate-regulated electric revenues [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 4 3 8 3
Rate-regulated electric revenues [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 334 299 752 662
Rate-regulated electric revenues [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 70 60 151 129
Rate-regulated electric revenues [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 129 108 260 213
Rate-regulated electric revenues [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 7 7 14 13
Rate-regulated electric revenues [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 99 87 196 165
Rate-regulated electric revenues [Member] | Pepco Holdings LLC [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1,199 1,071 2,522 2,195
Rate-regulated electric revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1,199 1,074 2,526 2,202
Revenue from Related Parties 2 4 6 7
Rate-regulated electric revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 2 1 2 0
Rate-regulated electric revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 548 537 1,200 1,142
Rate-regulated electric revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 140 124 281 242
Rate-regulated electric revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 332 257 655 505
Rate-regulated electric revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 15 17 31 30
Rate-regulated electric revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 164 139 359 283
Rate-regulated electric revenues [Member] | Potomac Electric Power Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 580 503 1,200 1,027
Rate-regulated electric revenues [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 581 503 1,201 1,030
Revenue from Related Parties 2 1 2 3
Rate-regulated electric revenues [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1 1 1 0
Rate-regulated electric revenues [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 234 223 509 476
Rate-regulated electric revenues [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 35 32 73 65
Rate-regulated electric revenues [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 250 188 503 372
Rate-regulated electric revenues [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 8 10 16 16
Rate-regulated electric revenues [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 54 50 100 101
Rate-regulated electric revenues [Member] | Delmarva Power and Light Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 295 262 643 562
Rate-regulated electric revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 296 264 645 566
Revenue from Related Parties 2 2 3 4
Rate-regulated electric revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1 0 1 0
Rate-regulated electric revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 155 147 362 337
Rate-regulated electric revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 51 46 107 92
Rate-regulated electric revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 30 22 56 43
Rate-regulated electric revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 3 3 7 7
Rate-regulated electric revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 57 46 113 87
Rate-regulated electric revenues [Member] | Atlantic City Electric Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 323 306 668 605
Rate-regulated electric revenues [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 324 307 670 606
Revenue from Related Parties 1 1 2 1
Rate-regulated electric revenues [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated electric revenues [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 159 167 329 329
Rate-regulated electric revenues [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 54 46 101 85
Rate-regulated electric revenues [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 52 47 96 90
Rate-regulated electric revenues [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 4 4 8 7
Rate-regulated electric revenues [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 55 43 136 95
Rate-regulated natural gas revenues [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 307 234 1,124 867
Rate-regulated natural gas revenues [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 301 231 1,106 872
Rate-regulated natural gas revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Transportation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | PECO Energy Co [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 108 82 414 310
Rate-regulated natural gas revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 108 83 413 311
Revenue from Related Parties 0 0 0 1
Rate-regulated natural gas revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 1 0
Rate-regulated natural gas revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 71 55 289 215
Rate-regulated natural gas revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 29 22 105 81
Rate-regulated natural gas revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Transportation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 6 5 14 12
Rate-regulated natural gas revenues [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 2 1 5 3
Rate-regulated natural gas revenues [Member] | Baltimore Gas and Electric Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 161 125 585 455
Rate-regulated natural gas revenues [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 161 127 588 462
Revenue from Related Parties 1 3 7 7
Rate-regulated natural gas revenues [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 2 1 3 1
Rate-regulated natural gas revenues [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 96 81 378 297
Rate-regulated natural gas revenues [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 18 13 63 48
Rate-regulated natural gas revenues [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 35 27 100 81
Rate-regulated natural gas revenues [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Transportation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 12 6 47 36
Rate-regulated natural gas revenues [Member] | Pepco Holdings LLC [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 37 24 120 94
Rate-regulated natural gas revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 37 24 120 94
Rate-regulated natural gas revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 17 12 68 57
Rate-regulated natural gas revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 8 6 29 24
Rate-regulated natural gas revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 3 1 6 3
Rate-regulated natural gas revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Transportation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 3 3 7 8
Rate-regulated natural gas revenues [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 6 2 10 2
Rate-regulated natural gas revenues [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Transportation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Delmarva Power and Light Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 37 24 120 95
Rate-regulated natural gas revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 37 24 120 95
Rate-regulated natural gas revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 17 12 68 57
Rate-regulated natural gas revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 8 6 29 24
Rate-regulated natural gas revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 3 1 6 3
Rate-regulated natural gas revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Transportation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 3 3 7 8
Rate-regulated natural gas revenues [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 6 2 10 3
Rate-regulated natural gas revenues [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Transportation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Rate-regulated natural gas revenues [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Alternative revenue programs [Member] | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 35 9 75 64
Alternative revenue programs [Member] | PECO Energy Co [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 7 6 17
Alternative revenue programs [Member] | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax (20) (10) (32) 8
Alternative revenue programs [Member] | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax (17) 41 (22) 88
Alternative revenue programs [Member] | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax (1) 19 (7) 46
Alternative revenue programs [Member] | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax (2) 10 (3) 19
Alternative revenue programs [Member] | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax $ (15) $ 12 $ (12) $ 23