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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, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Revenue, Major Customer [Line Items]        
Revenues $ 8,853 $ 8,929 $ 24,925 $ 26,096
Revenue from Related Parties 1 0 4 0
Commonwealth Edison Co [Member]        
Revenue, Major Customer [Line Items]        
Revenues 1,643 1,583 4,499 4,342
Revenue from Related Parties 15 4 31 13
Commonwealth Edison Co [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax (38) (56) (51) (98)
Commonwealth Edison Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 1,678 1,633 4,540 4,418
Commonwealth Edison Co [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues (35) (50) (41) (76)
PECO Energy Co [Member]        
Revenue, Major Customer [Line Items]        
Revenues 813 778 2,306 2,333
Revenue from Related Parties 3 1 7 4
PECO Energy Co [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 5 (11) 10 (16)
PECO Energy Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 808 785 2,293 2,338
PECO Energy Co [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues 5 (7) 13 (5)
PECO Energy Co [Member] | Rate-Regulated Electric Revenues [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Related Parties 3 1 6 4
PECO Energy Co [Member] | Rate-Regulated Natural Gas Revenues [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Related Parties 0 0 1 0
Baltimore Gas and Electric Company [Member]        
Revenue, Major Customer [Line Items]        
Revenues 731 703 2,284 2,327
Revenue from Related Parties 6 6 16 18
Baltimore Gas and Electric Company [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax (9) (5) (10) 11
Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 740 704 2,290 2,303
Baltimore Gas and Electric Company [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues (9) (1) (6) 24
Baltimore Gas and Electric Company [Member] | Rate-Regulated Electric Revenues [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Related Parties 3 2 9 5
Baltimore Gas and Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Related Parties 3 4 7 13
Pepco Holdings LLC [Member]        
Revenue, Major Customer [Line Items]        
Revenues 1,368 1,380 3,554 3,700
Revenue from Related Parties 6 4 13 11
Pepco Holdings LLC [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 31 (9) (15) 4
Pepco Holdings LLC [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 1,337 1,386 3,567 3,689
Pepco Holdings LLC [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues 31 (6) (13) 11
Potomac Electric Power Company [Member]        
Revenue, Major Customer [Line Items]        
Revenues 611 642 1,650 1,748
Revenue from Related Parties 3 2 6 5
Potomac Electric Power Company [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 18 (3) 20 10
Potomac Electric Power Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 593 643 1,629 1,732
Potomac Electric Power Company [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues 18 (1) 21 16
Delmarva Power and Light Company [Member]        
Revenue, Major Customer [Line Items]        
Revenues 337 319 954 987
Revenue from Related Parties 3 1 7 5
Delmarva Power and Light Company [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 8 (6) (15) (6)
Delmarva Power and Light Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 329 325 968 991
Delmarva Power and Light Company [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues 8 (6) (14) (4)
Atlantic City Electric Company [Member]        
Revenue, Major Customer [Line Items]        
Revenues 420 419 952 966
Revenue from Related Parties 1 1 3 2
Atlantic City Electric Company [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 5 1 (20) 0
Atlantic City Electric Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenues 415 418 972 966
Atlantic City Electric Company [Member] | Other Regulated Revenue [Member]        
Revenue, Major Customer [Line Items]        
Revenues 5 1 (20) 0
Electricity, US Regulated        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 4,365 4,268 11,585 11,609
Electricity, US Regulated | Commonwealth Edison Co [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1,666 1,635 4,519 4,427
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1,678 1,633 4,540 4,418
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 3 6 10 22
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 920 865 2,389 2,221
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 379 393 1,067 1,103
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 135 141 388 399
Electricity, US Regulated | 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 10 12 33 35
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 234 222 663 660
Electricity, US Regulated | PECO Energy Co [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 751 726 1,931 1,914
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 753 723 1,934 1,907
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 4 3 10
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 518 479 1,277 1,231
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 104 109 291 304
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 66 63 174 163
Electricity, US Regulated | 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 9 21 23
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 58 63 171 186
Electricity, US Regulated | Baltimore Gas and Electric Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 649 623 1,775 1,814
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 652 621 1,781 1,809
Electricity, US Regulated | 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 0 3 3 10
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 389 352 1,034 1,019
Electricity, US Regulated | 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 65 64 183 193
Electricity, US Regulated | 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 113 116 311 335
Electricity, US Regulated | 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
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 78 82 233 242
Electricity, US Regulated | Pepco Holdings LLC [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1,308 1,365 3,440 3,570
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1,314 1,366 3,451 3,574
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Operating Segment [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 3 2 7
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 763 741 1,825 1,816
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 134 147 355 387
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 262 297 755 843
Electricity, US Regulated | 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 14 17 45 47
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 141 164 471 481
Electricity, US Regulated | Potomac Electric Power Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 590 643 1,624 1,733
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 593 643 1,629 1,732
Electricity, US Regulated | 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 2 1 6
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 307 311 779 792
Electricity, US Regulated | 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 36 41 101 114
Electricity, US Regulated | 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 195 222 558 633
Electricity, US Regulated | 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 11 25 27
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 47 58 166 166
Electricity, US Regulated | Delmarva Power and Light Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 303 304 846 872
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 306 305 852 876
Electricity, US Regulated | 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 1 1
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 193 178 501 499
Electricity, US Regulated | 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 45 48 127 141
Electricity, US Regulated | 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 21 26 66 75
Electricity, US Regulated | 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 10 10
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 44 50 148 151
Electricity, US Regulated | Atlantic City Electric Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 414 417 969 964
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 415 418 972 966
Electricity, US Regulated | 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
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 263 252 545 525
Electricity, US Regulated | 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 53 58 127 132
Electricity, US Regulated | 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 46 49 131 135
Electricity, US Regulated | 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 10 10
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 50 56 159 164
Natural Gas, US Regulated        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 159 163 990 1,046
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 0 0 0 0
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | PECO Energy Co [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 54 62 358 431
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 55 62 359 431
Natural Gas, US Regulated | 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 0 1
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 32 38 252 285
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 16 17 86 122
Natural Gas, US Regulated | 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 1
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Transportation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 6 5 18 18
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1 2 3 5
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 85 79 503 484
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 88 83 509 494
Natural Gas, US Regulated | 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 0 1 1 3
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 55 49 342 327
Natural Gas, US Regulated | 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 9 9 55 55
Natural Gas, US Regulated | 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 21 20 96 93
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 3 5 16 19
Natural Gas, US Regulated | Pepco Holdings LLC [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 23 20 116 115
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 23 20 116 115
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 11 9 68 64
Natural Gas, US Regulated | 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 4 30 30
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 1 1 3 4
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Transportation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 3 4 10 11
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 2 2 5 6
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | Delmarva Power and Light Company [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 23 20 116 116
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 23 20 116 115
Natural Gas, US Regulated | 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 1
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Residential [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 11 9 68 64
Natural Gas, US Regulated | 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 4 30 30
Natural Gas, US Regulated | 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 1 1 3 4
Natural Gas, US Regulated | 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 4 10 11
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Other [Member]        
Revenue, Major Customer [Line Items]        
Revenue from Contract with Customer, Including Assessed Tax 2 2 5 6
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | 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
Natural Gas, US Regulated | 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