XML 254 R136.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Income Taxes - Reconciliation to Effective Tax Rate (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Mar. 23, 2016 | Dec. 31, 2016 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate [Line Items] |  |  |  |  |  |  |  |  |
U.S. Federal statutory rate |  |  |  | 21.00% |  | 35.00% |  | 35.00% |
State income taxes, net of Federal income tax benefit |  |  |  | 0.60% |  | 2.30% |  | 3.30% | [1]
Qualified nuclear decommissioning trust fund income |  |  |  | (1.90%) |  | 3.80% |  | 3.40% |
Amortization of investment tax credit, including deferred taxes on basis difference |  |  |  | (1.20%) |  | (0.90%) |  | (1.20%) |
Plant basis differences |  |  |  | (3.50%) | [2] | (1.70%) |  | (4.90%) |
Production tax credits and other credits |  |  |  | (2.20%) |  | (1.80%) |  | (3.60%) |
Noncontrolling interests |  |  |  | (1.00%) |  |  |  | (0.20%) |
Like-Kind Exchange |  |  |  | (8.30%) |  | (1.20%) |  |  |
Statute of limitations expiration |  |  |  |  |  |  |  | (0.40%) |
Penalties |  |  |  |  |  |  |  | 1.90% |
Merger expenses |  |  |  |  |  | (3.60%) |  | 5.60% |
FitzPatrick bargain purchase gain |  |  |  |  |  | (2.20%) |  |  |
Tax Cuts and Jobs Act of 2017 | [3] |  |  | 0.90% |  | (33.10%) |  |  |
Other |  |  |  | 1.00% |  | 0.10% |  | (0.70%) | [4]
Effective income tax rate |  |  |  | 5.40% |  | (3.30%) |  | 38.20% |
Amount of Impairment to Carrying Amount of Regulatory Assets |  |  |  |  |  | $ 35 |  |  |
Exelon Generation Co L L C [Member] |  |  |  |  |  |  |  |  |
Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate [Line Items] |  |  |  |  |  |  |  |  |
U.S. Federal statutory rate |  |  |  | 21.00% |  | 35.00% |  | 35.00% |
State income taxes, net of Federal income tax benefit |  |  |  | (16.60%) |  | 2.90% |  | 3.20% | [1]
Qualified nuclear decommissioning trust fund income |  |  |  | (11.80%) |  | 9.90% |  | 7.90% |
Amortization of investment tax credit, including deferred taxes on basis difference |  |  |  | (6.50%) |  | (2.10%) |  | (2.30%) |
Plant basis differences |  |  |  | (0.00%) | [2] | (0.00%) | [2] | (0.00%) |
Production tax credits and other credits |  |  |  | (13.50%) |  | (4.70%) |  | (8.30%) |
Noncontrolling interests |  |  |  | (6.10%) |  |  |  | (0.60%) |
Like-Kind Exchange |  |  |  | 0.00% |  | 0.00% |  |  |
Statute of limitations expiration |  |  |  |  |  |  |  | (1.70%) |
Penalties |  |  |  |  |  |  |  | 0.00% |
Merger expenses |  |  |  |  |  | (1.20%) |  | 1.10% |
FitzPatrick bargain purchase gain |  |  |  |  |  | (5.60%) |  |  |
Tax Cuts and Jobs Act of 2017 | [3] |  |  | 2.70% |  | (128.30%) |  |  |
Other |  |  |  | 1.30% |  | (0.50%) |  | (1.40%) | [4]
Effective income tax rate |  |  |  | (29.50%) |  | (94.60%) |  | 32.90% |
Commonwealth Edison Co [Member] |  |  |  |  |  |  |  |  |
Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate [Line Items] |  |  |  |  |  |  |  |  |
U.S. Federal statutory rate |  |  |  | 21.00% |  | 35.00% |  | 35.00% |
State income taxes, net of Federal income tax benefit |  |  |  | 8.30% |  | 5.70% |  | 5.60% | [1]
Qualified nuclear decommissioning trust fund income |  |  |  | 0.00% |  | 0.00% |  | 0.00% |
Amortization of investment tax credit, including deferred taxes on basis difference |  |  |  | (0.20%) |  | (0.20%) |  | (0.30%) |
Plant basis differences |  |  |  | (0.20%) | [2] | 0.30% | [2] | (0.60%) |
Production tax credits and other credits |  |  |  | (0.00%) |  | (0.00%) |  | (0.00%) |
Noncontrolling interests |  |  |  | (0.00%) |  |  |  | (0.00%) |
Like-Kind Exchange |  |  |  | (9.10%) |  | 1.30% |  |  |
Statute of limitations expiration |  |  |  |  |  |  |  | 0.00% |
Penalties |  |  |  |  |  |  |  | 4.50% |
Merger expenses |  |  |  |  |  | 0.00% |  | 0.00% |
FitzPatrick bargain purchase gain |  |  |  |  |  | 0.00% |  |  |
Tax Cuts and Jobs Act of 2017 | [3] |  |  | (0.10%) |  | 0.10% |  |  |
Other |  |  |  | 0.50% |  | 0.20% |  | 0.10% | [4]
Effective income tax rate |  |  |  | 20.20% |  | 42.40% |  | 44.30% |
Amount of Impairment to Carrying Amount of Regulatory Assets |  |  |  |  |  | $ 3 |  |  |
PECO Energy Co [Member] |  |  |  |  |  |  |  |  |
Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate [Line Items] |  |  |  |  |  |  |  |  |
U.S. Federal statutory rate |  |  |  | 21.00% |  | 35.00% |  | 35.00% |
State income taxes, net of Federal income tax benefit |  |  |  | (2.60%) |  | 0.60% |  | 1.30% | [1]
Qualified nuclear decommissioning trust fund income |  |  |  | 0.00% |  | 0.00% |  | 0.00% |
Amortization of investment tax credit, including deferred taxes on basis difference |  |  |  | (0.10%) |  | (0.10%) |  | (0.10%) |
Plant basis differences |  |  |  | (14.10%) | [2] | (13.80%) | [2] | (9.60%) |
Production tax credits and other credits |  |  |  | (0.00%) |  | (0.00%) |  | (0.00%) |
Noncontrolling interests |  |  |  | (0.00%) |  |  |  | (0.00%) |
Like-Kind Exchange |  |  |  | (3.20%) |  | 0.00% |  |  |
Statute of limitations expiration |  |  |  |  |  |  |  | 0.00% |
Penalties |  |  |  |  |  |  |  | 0.00% |
Merger expenses |  |  |  |  |  | 0.00% |  | 0.00% |
FitzPatrick bargain purchase gain |  |  |  |  |  | 0.00% |  |  |
Tax Cuts and Jobs Act of 2017 | [3] |  |  | 0.00% |  | (2.30%) |  |  |
Other |  |  |  | 0.30% |  | (0.10%) |  | (1.20%) | [4]
Effective income tax rate |  |  |  | 1.30% |  | 19.30% |  | 25.40% |
Baltimore Gas and Electric Company [Member] |  |  |  |  |  |  |  |  |
Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate [Line Items] |  |  |  |  |  |  |  |  |
U.S. Federal statutory rate |  |  |  | 21.00% |  | 35.00% |  | 35.00% |
State income taxes, net of Federal income tax benefit |  |  |  | 6.60% |  | 5.40% |  | 5.00% | [1]
Qualified nuclear decommissioning trust fund income |  |  |  | 0.00% |  | 0.00% |  | 0.00% |
Amortization of investment tax credit, including deferred taxes on basis difference |  |  |  | (0.10%) |  | (0.10%) |  | (0.10%) |
Plant basis differences |  |  |  | (1.30%) | [2] | 0.10% | [2] | (2.70%) |
Production tax credits and other credits |  |  |  | (0.00%) |  | (0.00%) |  | (0.00%) |
Noncontrolling interests |  |  |  | (0.00%) |  |  |  | (0.00%) |
Like-Kind Exchange |  |  |  | (8.00%) |  | 0.00% |  |  |
Statute of limitations expiration |  |  |  |  |  |  |  | 0.00% |
Penalties |  |  |  |  |  |  |  | 0.00% |
Merger expenses |  |  |  |  |  | 0.00% |  | 0.00% |
FitzPatrick bargain purchase gain |  |  |  |  |  | 0.00% |  |  |
Tax Cuts and Jobs Act of 2017 | [3] |  |  | 0.00% |  | 0.90% |  |  |
Other |  |  |  | 0.90% |  | 0.20% |  | 0.00% | [4]
Effective income tax rate |  |  |  | 19.10% |  | 41.50% |  | 37.20% |
Amount of Impairment to Carrying Amount of Regulatory Assets |  |  |  |  |  | $ 5 |  |  |
Potomac Electric Power Company [Member] |  |  |  |  |  |  |  |  |
Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate [Line Items] |  |  |  |  |  |  |  |  |
U.S. Federal statutory rate |  |  |  | 21.00% |  | 35.00% |  | 35.00% |
State income taxes, net of Federal income tax benefit |  |  |  | 2.20% |  | 3.20% |  | 15.70% | [1]
Qualified nuclear decommissioning trust fund income |  |  |  | 0.00% |  | 0.00% |  | 0.00% |
Amortization of investment tax credit, including deferred taxes on basis difference |  |  |  | (0.10%) |  | (0.10%) |  | (0.20%) |
Plant basis differences |  |  |  | (2.70%) | [2] | (0.40%) | [2] | (22.80%) |
Production tax credits and other credits |  |  |  | (0.00%) |  | (0.00%) |  | (0.00%) |
Noncontrolling interests |  |  |  | (0.00%) |  |  |  | (0.00%) |
Like-Kind Exchange |  |  |  | (14.80%) |  | 0.00% |  |  |
Statute of limitations expiration |  |  |  |  |  |  |  | 0.00% |
Penalties |  |  |  |  |  |  |  | 0.00% |
Merger expenses |  |  |  |  |  | (6.30%) |  | 23.50% |
FitzPatrick bargain purchase gain |  |  |  |  |  | 0.00% |  |  |
Tax Cuts and Jobs Act of 2017 | [3] |  |  | 0.00% |  | 2.70% |  |  |
Other |  |  |  | 0.20% |  | (0.20%) |  | (1.80%) | [4]
Effective income tax rate |  |  |  | 5.80% |  | 33.90% |  | 49.40% |
Amount of Impairment to Carrying Amount of Regulatory Assets |  |  |  |  |  | $ 14 |  |  |
Delmarva Power & Light Company [Member] |  |  |  |  |  |  |  |  |
Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate [Line Items] |  |  |  |  |  |  |  |  |
U.S. Federal statutory rate |  |  |  | 21.00% |  | 35.00% |  | 35.00% | [5]
State income taxes, net of Federal income tax benefit |  |  |  | 6.70% |  | 5.40% |  | 52.70% | [1],[5]
Qualified nuclear decommissioning trust fund income |  |  |  | 0.00% |  | 0.00% |  | 0.00% | [5]
Amortization of investment tax credit, including deferred taxes on basis difference |  |  |  | (0.30%) |  | (0.20%) |  | (3.70%) | [5]
Plant basis differences |  |  |  | (0.30%) | [2] | 2.00% | [2] | (25.50%) | [5]
Production tax credits and other credits |  |  |  | (0.00%) |  | (0.00%) |  | (0.00%) | [5]
Noncontrolling interests |  |  |  | (0.00%) |  |  |  | (0.00%) | [5]
Like-Kind Exchange |  |  |  | (12.00%) |  | 0.00% |  |  |
Statute of limitations expiration | [5] |  |  |  |  |  |  | 0.00% |
Penalties | [5] |  |  |  |  |  |  | 0.00% |
Merger expenses |  |  |  |  |  | (7.80%) |  | 112.90% | [5]
FitzPatrick bargain purchase gain |  |  |  |  |  | 0.00% |  |  |
Tax Cuts and Jobs Act of 2017 | [3] |  |  | 0.00% |  | 2.50% |  |  |
Other |  |  |  | 0.40% |  | 0.10% |  | (2.20%) | [4],[5]
Effective income tax rate |  |  |  | 15.50% |  | 37.00% |  | 169.20% | [5]
Amount of Impairment to Carrying Amount of Regulatory Assets |  |  |  |  |  | $ 6 |  |  |
Atlantic City Electric Company [Member] |  |  |  |  |  |  |  |  |
Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate [Line Items] |  |  |  |  |  |  |  |  |
U.S. Federal statutory rate |  |  |  | 21.00% |  | 35.00% |  | 35.00% | [5]
State income taxes, net of Federal income tax benefit |  |  |  | 7.40% |  | 5.60% |  | 6.20% | [1],[5]
Qualified nuclear decommissioning trust fund income |  |  |  | 0.00% |  | 0.00% |  | 0.00% | [5]
Amortization of investment tax credit, including deferred taxes on basis difference |  |  |  | (0.40%) |  | (0.40%) |  | 0.80% | [5]
Plant basis differences |  |  |  | (0.50%) | [2] | 3.60% | [2] | 10.30% | [5]
Production tax credits and other credits |  |  |  | (0.00%) |  | (0.00%) |  | (0.00%) | [5]
Noncontrolling interests |  |  |  | (0.00%) |  |  |  | (0.00%) | [5]
Like-Kind Exchange |  |  |  | (14.90%) |  | 0.00% |  |  |
Statute of limitations expiration | [5] |  |  |  |  |  |  | 0.00% |
Penalties | [5] |  |  |  |  |  |  | 0.00% |
Merger expenses |  |  |  |  |  | (19.80%) |  | (44.90%) | [5]
FitzPatrick bargain purchase gain |  |  |  |  |  | 0.00% |  |  |
Tax Cuts and Jobs Act of 2017 | [3] |  |  | 0.00% |  | 1.60% |  |  |
Other |  |  |  | 1.20% |  | (0.40%) |  | 1.30% | [4],[5]
Effective income tax rate |  |  |  | 13.80% |  | 25.20% |  | 8.70% | [5]
Amount of Impairment to Carrying Amount of Regulatory Assets |  |  |  |  |  | $ 7 |  |  |
Pepco Holdings LLC [Member] |  |  |  |  |  |  |  |  |
Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate [Line Items] |  |  |  |  |  |  |  |  |
U.S. Federal statutory rate |  |  |  | 21.00% |  | 35.00% |  |  |
State income taxes, net of Federal income tax benefit |  |  |  | 3.00% |  | 4.80% |  |  |
Qualified nuclear decommissioning trust fund income |  |  |  | 0.00% |  | 0.00% |  |  |
Amortization of investment tax credit, including deferred taxes on basis difference |  |  |  | (0.20%) |  | (0.20%) |  |  |
Plant basis differences | [2] |  |  | (1.60%) |  | 1.10% |  |  |
Production tax credits and other credits |  |  |  | (0.00%) |  | (0.00%) |  |  |
Noncontrolling interests |  |  |  | (0.00%) |  |  |  |  |
Like-Kind Exchange |  |  |  | (14.50%) |  | 0.00% |  |  |
Merger expenses |  |  |  |  |  | (9.50%) |  |  |
FitzPatrick bargain purchase gain |  |  |  |  |  | 0.00% |  |  |
Tax Cuts and Jobs Act of 2017 | [3] |  |  | 0.10% |  | 6.40% |  |  |
Other |  |  |  | 0.30% |  | (0.10%) |  |  |
Effective income tax rate |  |  |  | 8.10% |  | 37.50% |  |  |
Amount of Impairment to Carrying Amount of Regulatory Assets |  |  |  |  |  | $ 27 |  |  |
Pepco Holdings LLC [Member] | Successor [Member] |  |  |  |  |  |  |  |  |
Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate [Line Items] |  |  |  |  |  |  |  |  |
U.S. Federal statutory rate | [5] |  | 35.00% |  |  |  |  |  |
State income taxes, net of Federal income tax benefit | [1],[5] |  | 5.80% |  |  |  |  |  |
Qualified nuclear decommissioning trust fund income | [5] |  | 0.00% |  |  |  |  |  |
Amortization of investment tax credit, including deferred taxes on basis difference | [5] |  | 1.40% |  |  |  |  |  |
Plant basis differences | [5] |  | 39.00% |  |  |  |  |  |
Production tax credits and other credits | [5] |  | (0.00%) |  |  |  |  |  |
Noncontrolling interests | [5] |  | (0.00%) |  |  |  |  |  |
Statute of limitations expiration | [5] |  | 0.00% |  |  |  |  |  |
Penalties | [5] |  | (0.70%) |  |  |  |  |  |
Merger expenses | [5] |  | (89.00%) |  |  |  |  |  |
Other | [4],[5] |  | 3.30% |  |  |  |  |  |
Effective income tax rate | [5] |  | (5.20%) |  |  |  |  |  |
Pepco Holdings LLC [Member] | Predecessor [Member] |  |  |  |  |  |  |  |  |
Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate [Line Items] |  |  |  |  |  |  |  |  |
U.S. Federal statutory rate |  | 35.00% |  |  |  |  |  |  |
State income taxes, net of Federal income tax benefit | [1] | 11.90% |  |  |  |  |  |  |
Qualified nuclear decommissioning trust fund income |  | 0.00% |  |  |  |  |  |  |
Amortization of investment tax credit, including deferred taxes on basis difference |  | (0.90%) |  |  |  |  |  |  |
Plant basis differences |  | (13.50%) |  |  |  |  |  |  |
Production tax credits and other credits |  | (0.00%) |  |  |  |  |  |  |
Noncontrolling interests |  | (0.00%) |  |  |  |  |  |  |
Statute of limitations expiration |  | 0.00% |  |  |  |  |  |  |
Penalties |  | 0.00% |  |  |  |  |  |  |
Merger expenses |  | 11.10% |  |  |  |  |  |  |
Other | [4] | 3.60% |  |  |  |  |  |  |
Effective income tax rate |  | 47.20% |  |  |  |  |  |  |
[1] | Includes a remeasurement of uncertain state income tax positions for Pepco and DPL.
[2] | Includes the charges related to the transmission-related income tax regulatory asset for Exelon, ComEd, BGE, PHI, Pepco, DPL and ACE of $35 million, $3 million, $5 million, $27 million, $14 million, $6 million and $7 million, respectively. See Note 4 - Regulatory Matters for additional information.
[3] | Included are impacts for TCJA other than the corporate rate change, including revisions further limiting tax deductions for compensation of certain highest paid executives, the write-off of foreign tax credit carryforwards, and loss of a 2015 domestic production activities deduction due to an NOL carryback.
[4] | At PECO, includes a cumulative adjustment related to an anticipated gas repairs tax return accounting method change. The method change request was filed and accepted in 2017. No change to the results recorded as of December 31, 2016
[5] | DPL and ACE recognized a loss before income taxes for the year ended December 31, 2016, and PHI recognized a loss before income taxes for the period of March 24, 2016, through December 31, 2016. As a result, positive percentages represent an income tax benefit for the periods presented.

X
- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to acquisition of asset. + References No definition available. + Details
Name: | exc_EffectiveIncomeTaxRateReconciliationAcquisitionofAssetPercent
Namespace Prefix: | exc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate [Line Items] + References No definition available. + Details
Name: | exc_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRateLineItems
Namespace Prefix: | exc_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to cost associated with the merger or acquisition of a business. + References No definition available. + Details
Name: | exc_EffectiveIncomeTaxRateReconciliationMergerofBusinessPercent
Namespace Prefix: | exc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to cost associated with penalties. + References No definition available. + Details
Name: | exc_EffectiveIncomeTaxRateReconciliationPenaltiesPercent
Namespace Prefix: | exc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to qualified decommissioning investment income taxes paid. + References No definition available. + Details
Name: | exc_EffectiveIncomeTaxRateReconciliationQualifiedDecommissioningInvestmentIncomePercent
Namespace Prefix: | exc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Discloses the amount of any reduction to the carrying amounts of regulated assets that result from impairment (for example, rate actions of a regulator). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 35 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6066304&loc=d3e44026-110379 + Details
Name: | us-gaap_AmountOfImpairmentToCarryingAmountOfRegulatoryAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)(2)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 + Details
Name: | us-gaap_EffectiveIncomeTaxRateContinuingOperations
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 + Details
Name: | us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the income tax rates. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 + Details
Name: | us-gaap_EffectiveIncomeTaxRateReconciliationChangeInEnactedTaxRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to other deductions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 + Details
Name: | us-gaap_EffectiveIncomeTaxRateReconciliationDeductionsOther
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to noncontrolling interest income (loss) exempt from income taxes. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 + Details
Name: | us-gaap_EffectiveIncomeTaxRateReconciliationMinorityInterestIncomeExpense
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to other adjustments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 + Details
Name: | us-gaap_EffectiveIncomeTaxRateReconciliationOtherAdjustments
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 + Details
Name: | us-gaap_EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to investment tax credit. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 + Details
Name: | us-gaap_EffectiveIncomeTaxRateReconciliationTaxCreditsInvestment
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to other tax credits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 + Details
Name: | us-gaap_EffectiveIncomeTaxRateReconciliationTaxCreditsOther
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to income tax settlements. Including, but not limited to, domestic tax settlement, foreign tax settlement, state and local tax settlement, and other tax settlements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 + Details
Name: | us-gaap_EffectiveIncomeTaxRateReconciliationTaxSettlements
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to other income tax settlements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 + Details
Name: | us-gaap_EffectiveIncomeTaxRateReconciliationTaxSettlementsOther
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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

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

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

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

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

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

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

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

X
- Details
Name: | us-gaap_StatementScenarioAxis=us-gaap_SuccessorMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementScenarioAxis=us-gaap_PredecessorMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |