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Regulatory Matters Regulatory Matters - Schedule of Regulatory Assets (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017 | Jun. 30, 2017
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Regulatory Assets [Line Items] |  |  |
Regulatory Assets | $ 9,459 | $ 9,288 |
Current regulatory assets | 1,222 | 1,267 |
Noncurrent regulatory assets | 8,237 | 8,021 |
Pension and Other Postretirement Plans Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 2,455 |
Pension and Post Retirement Plan Merger Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 1,266 | 1,393 |
Deferred income taxes |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 414 | 306 |
Advanced Metering Infrastructure Deployment Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 202 | 385 |
Advanced Metering Infrastructure Legacy Meter Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 328 | 223 |
Advanced Metering Infrastructure Incremental Deployment Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 32 | 32 |
Electric Distribution Formula Rate Annual Reconciliations [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 158 | 186 |
Electric Distribution Formula Rate One-time Events [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 81 | 58 |
Energy efficiency costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 472 | 166 |
Fair value of long-term debt |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 758 |
Fair value of PHI's unamortized energy contracts |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 561 | 750 |
Asset retirement obligations |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 118 | 109 |
MGP remediation costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 326 | 295 |
Renewable Energy Program [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 249 | 258 |
Electric Energy and Natural Gas Costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 193 | 47 |
Under Recovered Transmission Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 41 | 35 |
Energy efficiency and demand response programs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 545 | 596 |
Merger integration costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 42 | 45 |
Under-recovered revenue decoupling |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 59 | 55 |
Securitized stranded costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 50 | 79 |
Removal costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 564 | 529 |
DC PLUG charge |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 159 | 190 |
Storm Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 41 | 27 |
Other |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 303 | 311 |
Commonwealth Edison Co [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 1,279 |
Current regulatory assets | 293 | 225 |
Noncurrent regulatory assets | 1,307 | 1,054 |
Commonwealth Edison Co [Member] | Pension and Other Postretirement Plans Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
Commonwealth Edison Co [Member] | Pension and Post Retirement Plan Merger Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Commonwealth Edison Co [Member] | Deferred income taxes |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
Commonwealth Edison Co [Member] | Advanced Metering Infrastructure Deployment Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Commonwealth Edison Co [Member] | Advanced Metering Infrastructure Legacy Meter Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 136 | 155 |
Commonwealth Edison Co [Member] | Advanced Metering Infrastructure Incremental Deployment Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Commonwealth Edison Co [Member] | Electric Distribution Formula Rate Annual Reconciliations [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 158 | 186 |
Commonwealth Edison Co [Member] | Electric Distribution Formula Rate One-time Events [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 81 | 58 |
Commonwealth Edison Co [Member] | Energy efficiency costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 166 |
Commonwealth Edison Co [Member] | Fair value of long-term debt |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
Commonwealth Edison Co [Member] | Fair value of PHI's unamortized energy contracts |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
Commonwealth Edison Co [Member] | Asset retirement obligations |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 79 | 73 |
Commonwealth Edison Co [Member] | MGP remediation costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 309 | 273 |
Commonwealth Edison Co [Member] | Renewable Energy Program [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 256 |
Commonwealth Edison Co [Member] | Electric Energy and Natural Gas Costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
Commonwealth Edison Co [Member] | Under Recovered Transmission Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 6 | 6 |
Commonwealth Edison Co [Member] | Energy efficiency and demand response programs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
Commonwealth Edison Co [Member] | Merger integration costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
Commonwealth Edison Co [Member] | Under-recovered revenue decoupling |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
Commonwealth Edison Co [Member] | Securitized stranded costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
Commonwealth Edison Co [Member] | Removal costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
Commonwealth Edison Co [Member] | DC PLUG charge |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
Commonwealth Edison Co [Member] | Storm Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Commonwealth Edison Co [Member] | Other |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 106 |
PECO Energy Co [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 410 |
Current regulatory assets | 81 | 29 |
Noncurrent regulatory assets | 460 | 381 |
PECO Energy Co [Member] | Pension and Other Postretirement Plans Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
PECO Energy Co [Member] | Pension and Post Retirement Plan Merger Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
PECO Energy Co [Member] | Deferred income taxes |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 297 |
PECO Energy Co [Member] | Advanced Metering Infrastructure Deployment Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
PECO Energy Co [Member] | Advanced Metering Infrastructure Legacy Meter Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 36 |
PECO Energy Co [Member] | Advanced Metering Infrastructure Incremental Deployment Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
PECO Energy Co [Member] | Electric Distribution Formula Rate Annual Reconciliations [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
PECO Energy Co [Member] | Electric Distribution Formula Rate One-time Events [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
PECO Energy Co [Member] | Energy efficiency costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
PECO Energy Co [Member] | Fair value of long-term debt |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
PECO Energy Co [Member] | Fair value of PHI's unamortized energy contracts |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
PECO Energy Co [Member] | Asset retirement obligations |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 22 |
PECO Energy Co [Member] | MGP remediation costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 22 |
PECO Energy Co [Member] | Renewable Energy Program [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
PECO Energy Co [Member] | Electric Energy and Natural Gas Costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 1 |
PECO Energy Co [Member] | Under Recovered Transmission Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
PECO Energy Co [Member] | Energy efficiency and demand response programs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 1 |
PECO Energy Co [Member] | Merger integration costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
PECO Energy Co [Member] | Under-recovered revenue decoupling |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
PECO Energy Co [Member] | Securitized stranded costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
PECO Energy Co [Member] | Removal costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
PECO Energy Co [Member] | DC PLUG charge |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
PECO Energy Co [Member] | Storm Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
PECO Energy Co [Member] | Other |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 31 |
Baltimore Gas and Electric Company [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 571 |
Current regulatory assets | 177 | 174 |
Noncurrent regulatory assets | 398 | 397 |
Baltimore Gas and Electric Company [Member] | Pension and Other Postretirement Plans Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Baltimore Gas and Electric Company [Member] | Pension and Post Retirement Plan Merger Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Baltimore Gas and Electric Company [Member] | Deferred income taxes |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
Baltimore Gas and Electric Company [Member] | Advanced Metering Infrastructure Deployment Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 129 |
Baltimore Gas and Electric Company [Member] | Advanced Metering Infrastructure Legacy Meter Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 48 | 53 | $ 56
Baltimore Gas and Electric Company [Member] | Advanced Metering Infrastructure Incremental Deployment Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 32 | 32 |
Baltimore Gas and Electric Company [Member] | Electric Distribution Formula Rate Annual Reconciliations [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Baltimore Gas and Electric Company [Member] | Electric Distribution Formula Rate One-time Events [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Baltimore Gas and Electric Company [Member] | Energy efficiency costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Baltimore Gas and Electric Company [Member] | Fair value of long-term debt |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Baltimore Gas and Electric Company [Member] | Fair value of PHI's unamortized energy contracts |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Baltimore Gas and Electric Company [Member] | Asset retirement obligations |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 14 |
Baltimore Gas and Electric Company [Member] | MGP remediation costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
Baltimore Gas and Electric Company [Member] | Renewable Energy Program [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
Baltimore Gas and Electric Company [Member] | Electric Energy and Natural Gas Costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 16 |
Baltimore Gas and Electric Company [Member] | Under Recovered Transmission Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 4 | 7 |
Baltimore Gas and Electric Company [Member] | Energy efficiency and demand response programs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 285 |
Baltimore Gas and Electric Company [Member] | Merger integration costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 6 |
Baltimore Gas and Electric Company [Member] | Under-recovered revenue decoupling |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 14 |
Baltimore Gas and Electric Company [Member] | Securitized stranded costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 0 |
Baltimore Gas and Electric Company [Member] | Removal costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Baltimore Gas and Electric Company [Member] | DC PLUG charge |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Baltimore Gas and Electric Company [Member] | Storm Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Baltimore Gas and Electric Company [Member] | Other |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 15 |
Pepco Holdings LLC [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 3,047 |
Current regulatory assets | 489 | 554 |
Noncurrent regulatory assets | 2,312 | 2,493 |
Pepco Holdings LLC [Member] | Pension and Other Postretirement Plans Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Pepco Holdings LLC [Member] | Pension and Post Retirement Plan Merger Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Pepco Holdings LLC [Member] | Deferred income taxes |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 10 | 9 |
Pepco Holdings LLC [Member] | Advanced Metering Infrastructure Deployment Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 89 | 101 |
Pepco Holdings LLC [Member] | Advanced Metering Infrastructure Legacy Meter Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 120 | 134 |
Pepco Holdings LLC [Member] | Advanced Metering Infrastructure Incremental Deployment Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Pepco Holdings LLC [Member] | Electric Distribution Formula Rate Annual Reconciliations [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Pepco Holdings LLC [Member] | Electric Distribution Formula Rate One-time Events [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Pepco Holdings LLC [Member] | Energy efficiency costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Pepco Holdings LLC [Member] | Fair value of long-term debt |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 569 | 619 |
Pepco Holdings LLC [Member] | Fair value of PHI's unamortized energy contracts |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 561 | 750 |
Pepco Holdings LLC [Member] | Asset retirement obligations |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 1 | 0 |
Pepco Holdings LLC [Member] | MGP remediation costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Pepco Holdings LLC [Member] | Renewable Energy Program [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 2 |
Pepco Holdings LLC [Member] | Electric Energy and Natural Gas Costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 93 | 30 |
Pepco Holdings LLC [Member] | Under Recovered Transmission Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 31 | 22 |
Pepco Holdings LLC [Member] | Energy efficiency and demand response programs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 255 | 310 |
Pepco Holdings LLC [Member] | Merger integration costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 39 | 39 |
Pepco Holdings LLC [Member] | Under-recovered revenue decoupling |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 57 | 41 |
Pepco Holdings LLC [Member] | Securitized stranded costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 50 | 79 |
Pepco Holdings LLC [Member] | Removal costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 564 | 529 |
Pepco Holdings LLC [Member] | DC PLUG charge |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 159 | 190 |
Pepco Holdings LLC [Member] | Storm Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 41 | 27 |
Pepco Holdings LLC [Member] | Other |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 162 | 165 |
Potomac Electric Power Company [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 891 |
Current regulatory assets | 270 | 213 |
Noncurrent regulatory assets | 643 | 678 |
Potomac Electric Power Company [Member] | Pension and Other Postretirement Plans Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Potomac Electric Power Company [Member] | Pension and Post Retirement Plan Merger Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Potomac Electric Power Company [Member] | Deferred income taxes |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 10 | 9 |
Potomac Electric Power Company [Member] | Advanced Metering Infrastructure Deployment Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 50 | 58 |
Potomac Electric Power Company [Member] | Advanced Metering Infrastructure Legacy Meter Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 90 | 100 |
Potomac Electric Power Company [Member] | Advanced Metering Infrastructure Incremental Deployment Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Potomac Electric Power Company [Member] | Electric Distribution Formula Rate Annual Reconciliations [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Potomac Electric Power Company [Member] | Electric Distribution Formula Rate One-time Events [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Potomac Electric Power Company [Member] | Energy efficiency costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Potomac Electric Power Company [Member] | Fair value of long-term debt |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Potomac Electric Power Company [Member] | Fair value of PHI's unamortized energy contracts |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Potomac Electric Power Company [Member] | Asset retirement obligations |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 1 | 0 |
Potomac Electric Power Company [Member] | MGP remediation costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Potomac Electric Power Company [Member] | Renewable Energy Program [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Potomac Electric Power Company [Member] | Electric Energy and Natural Gas Costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 84 | 8 |
Potomac Electric Power Company [Member] | Under Recovered Transmission Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 10 | 3 |
Potomac Electric Power Company [Member] | Energy efficiency and demand response programs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 188 | 229 |
Potomac Electric Power Company [Member] | Merger integration costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 18 | 20 |
Potomac Electric Power Company [Member] | Under-recovered revenue decoupling |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 57 | 38 |
Potomac Electric Power Company [Member] | Securitized stranded costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Potomac Electric Power Company [Member] | Removal costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 158 | 150 |
Potomac Electric Power Company [Member] | DC PLUG charge |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 159 | 190 |
Potomac Electric Power Company [Member] | Storm Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 9 | 7 |
Potomac Electric Power Company [Member] | Other |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 79 | 79 |
Delmarva Power & Light Company [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 314 |
Current regulatory assets | 59 | 69 |
Noncurrent regulatory assets | 231 | 245 |
Delmarva Power & Light Company [Member] | Pension and Other Postretirement Plans Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Delmarva Power & Light Company [Member] | Pension and Post Retirement Plan Merger Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Delmarva Power & Light Company [Member] | Deferred income taxes |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Delmarva Power & Light Company [Member] | Advanced Metering Infrastructure Deployment Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 39 | 43 |
Delmarva Power & Light Company [Member] | Advanced Metering Infrastructure Legacy Meter Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 30 | 34 |
Delmarva Power & Light Company [Member] | Advanced Metering Infrastructure Incremental Deployment Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Delmarva Power & Light Company [Member] | Electric Distribution Formula Rate Annual Reconciliations [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Delmarva Power & Light Company [Member] | Electric Distribution Formula Rate One-time Events [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Delmarva Power & Light Company [Member] | Energy efficiency costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Delmarva Power & Light Company [Member] | Fair value of long-term debt |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Delmarva Power & Light Company [Member] | Fair value of PHI's unamortized energy contracts |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Delmarva Power & Light Company [Member] | Asset retirement obligations |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Delmarva Power & Light Company [Member] | MGP remediation costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Delmarva Power & Light Company [Member] | Renewable Energy Program [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 1 |
Delmarva Power & Light Company [Member] | Electric Energy and Natural Gas Costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 7 |
Delmarva Power & Light Company [Member] | Under Recovered Transmission Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 14 | 8 |
Delmarva Power & Light Company [Member] | Energy efficiency and demand response programs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 67 | 81 |
Delmarva Power & Light Company [Member] | Merger integration costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 11 | 10 |
Delmarva Power & Light Company [Member] | Under-recovered revenue decoupling |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 3 |
Delmarva Power & Light Company [Member] | Securitized stranded costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Delmarva Power & Light Company [Member] | Removal costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 97 | 93 |
Delmarva Power & Light Company [Member] | DC PLUG charge |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Delmarva Power & Light Company [Member] | Storm Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 4 | 5 |
Delmarva Power & Light Company [Member] | Other |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 28 | 29 |
Atlantic City Electric Company [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets |  | 430 |
Current regulatory assets | 40 | 71 |
Noncurrent regulatory assets | 386 | 359 |
Atlantic City Electric Company [Member] | Pension and Other Postretirement Plans Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Atlantic City Electric Company [Member] | Pension and Post Retirement Plan Merger Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Atlantic City Electric Company [Member] | Deferred income taxes |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Atlantic City Electric Company [Member] | Advanced Metering Infrastructure Deployment Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Atlantic City Electric Company [Member] | Advanced Metering Infrastructure Legacy Meter Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Atlantic City Electric Company [Member] | Advanced Metering Infrastructure Incremental Deployment Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Atlantic City Electric Company [Member] | Electric Distribution Formula Rate Annual Reconciliations [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Atlantic City Electric Company [Member] | Electric Distribution Formula Rate One-time Events [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Atlantic City Electric Company [Member] | Energy efficiency costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Atlantic City Electric Company [Member] | Fair value of long-term debt |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Atlantic City Electric Company [Member] | Fair value of PHI's unamortized energy contracts |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Atlantic City Electric Company [Member] | Asset retirement obligations |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Atlantic City Electric Company [Member] | MGP remediation costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Atlantic City Electric Company [Member] | Renewable Energy Program [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 1 |
Atlantic City Electric Company [Member] | Electric Energy and Natural Gas Costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 9 | 15 |
Atlantic City Electric Company [Member] | Under Recovered Transmission Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 7 | 11 |
Atlantic City Electric Company [Member] | Energy efficiency and demand response programs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Atlantic City Electric Company [Member] | Merger integration costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 10 | 9 |
Atlantic City Electric Company [Member] | Under-recovered revenue decoupling |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Atlantic City Electric Company [Member] | Securitized stranded costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 50 | 79 |
Atlantic City Electric Company [Member] | Removal costs |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 309 | 286 |
Atlantic City Electric Company [Member] | DC PLUG charge |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 0 | 0 |
Atlantic City Electric Company [Member] | Storm Costs [Member] |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | 28 | 15 |
Atlantic City Electric Company [Member] | Other |  |  |
Regulatory Assets [Line Items] |  |  |
Regulatory Assets | $ 13 | $ 14 |

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