XML 203 R85.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Regulatory Matters Regulatory Matters - Schedule of Revenue Increases (Decreases) (Details) - Commonwealth Edison Co [Member] - USD ($) $ in Millions |  |  | 12 Months Ended
--- | --- | --- | ---
Dec. 04, 2018 | Apr. 16, 2018 | Dec. 31, 2018 | Dec. 31, 2017
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount | [1] |  |  | $ (44) |
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount | [1],[2] |  |  | (26) |
Electric Distribution [Member] |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount |  |  |  | $ (58) |
Public Utilities, Approved Rate Increase (Decrease), Amount |  |  |  |  | $ 34
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount | [3] | $ (24) | $ (23) |  |
Public Utilities, Requested Equity Capital Structure, Percentage |  | 8.69% |  |  |
[1] | The time period for any formal challenges to the annual transmission formula rate update filings expired with no formal challenges submitted.
[2] | {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOmVlYzRiNDIxOTkxNDRkN2ViNWYzYTRhOTVmMjFkNDYzfFRleHRTZWxlY3Rpb246MzY0MUFFQzNGNTE3Mzk3OTI2RjIxNTRFRUQyNkYyMzMM}
[3] | Includes the annual ongoing TCJA tax savings further discussed below.

X
- Definition Amount of public utility's approved rate increase (decrease) by regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesApprovedRateIncreaseDecreaseAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesGeneralDisclosuresLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of public utility's requested equity to capital, including debt and equity. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedEquityCapitalStructurePercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of public utility's amended requested rate increase (decrease) with regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmendedAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of public utility's requested rate increase (decrease) with regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=exc_CommonwealthEdisonCoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilityAxis=us-gaap_ElectricDistributionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |