XML 298 R180.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Changes in Accumulated Other Comprehensive Income - Components of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |
Other Comprehensive Income (Loss), Tax | $ (17) | $ (90) | $ 30
Prior service costs |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |
Other Comprehensive Income (Loss), Tax | 24 | 36 | 30
Actuarial losses |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |
Other Comprehensive Income (Loss), Tax | (86) | (128) | (118)
Pension and Non-Pension Postretirement Benefit Plan Items |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |
Other Comprehensive Income (Loss), Tax | 50 | 13 | 115
Gains and (Losses) on Cash Flow Hedges |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |
Other Comprehensive Income (Loss), Tax | (5) | (7) | 0
Unrealized Gains and (losses) on Marketable Securities |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |
Change in unrealized gains (losses) on investments in unconsolidated affiliates | 0 | (3) | 3
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax | 0 | (1) | 0
Exelon Generation Co L L C [Member] |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |
Other Comprehensive Income (Loss), Tax | (5) | (10) | 1
Exelon Generation Co L L C [Member] | Gains and (Losses) on Cash Flow Hedges |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |
Other Comprehensive Income (Loss), Tax | (4) | (6) | (2)
Exelon Generation Co L L C [Member] | Unrealized Gains and (losses) on Marketable Securities |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |
Change in unrealized gains (losses) on investments in unconsolidated affiliates | (1) | (3) | 3
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax | $ 0 | $ (1) | $ 0

X
- Definition Tax effect of the change in unrealized gains and losses from equity investments held during the period being reported on. + References No definition available. + Details
Name: | exc_OtherComprehensiveIncomeUnrealizedGainLossOnEquityInvestmentsArisingDuringPeriodTax
Namespace Prefix: | exc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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_AccumulatedOtherComprehensiveIncomeLossLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of tax expense (benefit) allocated to other comprehensive income (loss). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e640-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 20 -Section 45 -Paragraph 11 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=79507043&loc=d3e39076-109324 + Details
Name: | us-gaap_OtherComprehensiveIncomeLossTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of tax expense (benefit) before reclassification adjustments of unrealized holding gain (loss) on available-for-sale securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e640-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (e,f) -URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669646-108580 + Details
Name: | us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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