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Regulatory Matters - Maryland and New Jersey (Details) $ in Millions |  |  |  | 9 Months Ended | 33 Months Ended | 36 Months Ended
--- | --- | --- | --- | --- | --- | ---
Dec. 12, 2016 USD ($) | Jul. 16, 2015 | Feb. 27, 2013 USD ($) | Sep. 30, 2017 component | Sep. 30, 2017 USD ($) component | Dec. 31, 2020 USD ($) | Dec. 31, 2017 USD ($)
New Jersey |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |
Number of supply components | component |  |  |  | 2 | 2 |  |
PE | Maryland |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |
Incremental energy savings goal next 12 months |  | 0.97% |  |  |  |  |
Incremental energy savings goal thereafter |  | 0.20% |  |  |  |  |
Incremental energy savings goal |  | 2.00% |  |  |  |  |
Expenditures for cost recovery program incurred |  |  |  |  | $ 56 |  |
Recovery period for expenditures for cost recovery program |  | 5 years |  | 3 years |  |  |
Expected infrastructure investments |  |  | $ 2,700 |  |  |  |
Period of expected infrastructure investments |  |  | 15 years |  |  |  |
JCP&L | NJBPU | New Jersey |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |
Approved amount of annual increase | $ 80 |  |  |  |  |  |
Scenario, Forecast | PE | Maryland |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |
Expenditures for cost recovery program |  |  |  |  |  | $ 116 | $ 70
Recovery period for expenditures for cost recovery program |  |  |  |  |  | 3 years |

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