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Regulatory Matters - Maryland and New Jersey (Details) $ in Millions |  |  |  |  | 9 Months Ended | 36 Months Ended
--- | --- | --- | --- | --- | --- | ---
Nov. 02, 2016 USD ($) | Apr. 28, 2016 USD ($) | Jul. 16, 2015 | Feb. 27, 2013 USD ($) | Sep. 30, 2016 USD ($) component bgs | Dec. 31, 2017 USD ($)
Maryland |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |
Expenditures for cost recovery program incurred |  |  |  |  | $ 38.0 |
Incremental energy savings goal next 12 months (percent) |  |  | 0.20% |  |  |
Incremental energy savings goal thereafter (percent) |  |  | 2.00% |  |  |
Recovery period for expenditures for cost recovery program |  |  | 5 years |  | 3 years |
Expected infrastructure investments |  |  |  | $ 2,700.0 |  |
Period of expected infrastructure investments |  |  |  | 15 years |  |
New Jersey |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |
Number of supply components | component |  |  |  |  | 2 |
Number of basic generation services | bgs |  |  |  |  | 1 |
JCP&L | NJBPU | New Jersey |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |
Amount of requested rate increase (decrease) |  | $ 142.1 |  |  | $ 146.6 |
Scenario, Forecast | Maryland |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |
Expenditures for cost recovery program |  |  |  |  |  | $ 68.0
Subsequent Event | JCP&L | NJBPU | New Jersey |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |
Approved amount of annual increase | $ 80.0 |  |  |  |  |

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