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Segment Information - Electric and Gas Revenue by Customer Class (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2022
Sep. 30, 2021
Sep. 30, 2022
Sep. 30, 2021
Revenue, Major Customer [Line Items]        
Revenues $ 4,845 $ 4,863 $ 14,412 $ 13,514
Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenues 4,845 4,863 14,412 13,514
Revenue from Related Parties 0 36 6 48
Commonwealth Edison Co [Member]        
Revenue, Major Customer [Line Items]        
Revenues 1,378 1,789 4,536 4,840
Revenue from Related Parties 6 9 14 19
Commonwealth Edison Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 1,284 1,815 4,351 4,784
Commonwealth Edison Co [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues 94 (26) 185 56
PECO Energy Co [Member]        
Revenue, Major Customer [Line Items]        
Revenues 1,014 818 2,877 2,399
Revenue from Related Parties 3 2 5 6
PECO Energy Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 1,014 813 2,864 2,377
PECO Energy Co [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues 0 5 13 22
Baltimore Gas and Electric Company [Member]        
Revenue, Major Customer [Line Items]        
Revenues 870 770 2,810 2,426
Revenue from Related Parties 3 7 13 20
Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 873 790 2,835 2,434
Baltimore Gas and Electric Company [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues (3) (20) (25) (8)
Pepco Holdings LLC [Member]        
Revenue, Major Customer [Line Items]        
Revenues 1,598 1,470 4,223 3,854
Revenue from Related Parties 3 3 9 10
Pepco Holdings LLC [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 1,608 1,462 4,252 3,757
Pepco Holdings LLC [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues (10) 8 (29) 97
Potomac Electric Power Company [Member]        
Revenue, Major Customer [Line Items]        
Revenues 724 660 1,919 1,736
Revenue from Related Parties 2 2 4 4
Potomac Electric Power Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 731 650 1,931 1,680
Potomac Electric Power Company [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues (7) 10 (12) 56
Delmarva Power and Light Company [Member]        
Revenue, Major Customer [Line Items]        
Revenues 412 360 1,176 1,040
Revenue from Related Parties 1 2 5 6
Delmarva Power and Light Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 412 361 1,178 1,022
Delmarva Power and Light Company [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues 0 (1) (2) 18
Atlantic City Electric Company [Member]        
Revenue, Major Customer [Line Items]        
Revenues 462 451 1,120 1,080
Revenue from Related Parties 0 1 2 2
Atlantic City Electric Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 465 451 1,134 1,057
Atlantic City Electric Company [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues (3) 0 (14) 23
Rate-regulated electric revenues [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 4,557 4,736 12,972 12,344
Rate-regulated electric revenues [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 4,621 4,692 13,082 12,470
Rate-regulated electric revenues [Member] | Commonwealth Edison Co [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1,284 1,812 4,359 4,789
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 1,284 1,815 4,351 4,784
Revenue from Related Parties 6 9 14 19
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 6 6 22 24
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 935 978 2,610 2,479
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 217 433 953 1,176
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 (117) 148 48 420
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 3 11 22 33
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 246 245 718 676
Rate-regulated electric revenues [Member] | PECO Energy Co [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 943 757 2,384 2,008
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 941 757 2,378 2,011
Revenue from Related Parties 3 2 5 5
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 5 2 11 2
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 620 509 1,538 1,325
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 149 113 386 312
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 93 67 229 183
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 8 7 23 24
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 71 61 202 167
Rate-regulated electric revenues [Member] | Baltimore Gas and Electric Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 761 694 2,138 1,874
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 760 695 2,132 1,877
Revenue from Related Parties 2 4 5 10
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 11 7
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 406 383 1,158 1,044
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 88 73 239 202
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 158 128 418 342
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 20 20
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 101 104 297 269
Rate-regulated electric revenues [Member] | Pepco Holdings LLC [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1,568 1,438 4,090 3,632
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 1,570 1,439 4,095 3,639
Revenue from Related Parties 3 3 9 10
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 1 2 4 3
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 808 782 2,007 1,924
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 179 150 461 392
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 401 320 1,056 825
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 16 15 47 45
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 166 172 524 453
Rate-regulated electric revenues [Member] | Potomac Electric Power Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 730 649 1,930 1,678
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 731 650 1,931 1,680
Revenue from Related Parties 2 2 4 4
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 3 2
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 318 309 826 785
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 44 36 117 101
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 303 244 806 616
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 9 8 25 24
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 57 53 157 154
Rate-regulated electric revenues [Member] | Delmarva Power and Light Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 373 337 1,017 899
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 374 338 1,021 904
Revenue from Related Parties 1 2 5 6
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 0 1 1 1
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 207 198 570 535
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 65 53 173 145
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 43 27 99 70
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 4 4 11 11
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 55 56 168 143
Rate-regulated electric revenues [Member] | Atlantic City Electric Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 465 450 1,132 1,055
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 465 451 1,134 1,057
Revenue from Related Parties 0 1 2 2
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 283 275 611 604
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 70 61 171 146
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 55 49 151 139
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 3 3 11 10
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 54 63 190 158
Rate-regulated natural gas revenues [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 224 174 1,348 1,041
Rate-regulated natural gas revenues [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 224 171 1,330 1,044
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 73 56 487 365
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 73 56 486 366
Revenue from Related Parties 0 0 1 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 46 36 335 251
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 20 13 125 94
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 5 5 19 17
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 2 7 4
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 114 93 699 549
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 113 95 703 557
Revenue from Related Parties 1 3 7 10
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 1 1 4 2
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 70 57 448 354
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 13 10 77 59
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 28 22 128 103
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 2 6 50 41
Rate-regulated natural gas revenues [Member] | Pepco Holdings LLC [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 38 23 157 118
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 38 23 157 118
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 10 10 77 67
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 6 5 35 29
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 2 9 5
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 11 11
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 16 3 25 6
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 38 23 157 118
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 38 23 157 118
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 10 10 77 67
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 6 5 35 29
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 2 9 5
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 11 11
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 16 3 25 6
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 88 (32) 163 32
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 (5) 3 1 20
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 (8) (24) (40) (17)
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 (11) 6 (33) 94
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 (8) 9 (15) 54
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 0 (2) (3) 17
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 $ (3) $ 0 $ (14) $ 23