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Commitments and Contingencies Commitments and Contingencies - Schedule of Commercial Commitments (Details) $ in Millions | Dec. 31, 2018 USD ($)
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Guarantor Obligations [Line Items] |  |
Contractual Obligation | $ 3,507 |
Contractual Obligation, Due in Next Fiscal Year | 2,728 |
Contractual Obligation, Due in Second Year | 344 |
Contractual Obligation, Due in Third Year | 41 |
Contractual Obligation, Due in Fourth Year | 3 |
Contractual Obligation, Due in Fifth Year | 3 |
Contractual Obligation, Due after Fifth Year | 388 |
Guarantee obligations maximum exposure | 61 |
Exelon Generation Co L L C [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 2,900 |
Contractual Obligation, Due in Next Fiscal Year | 2,581 |
Contractual Obligation, Due in Second Year | 318 |
Contractual Obligation, Due in Third Year | 1 |
Contractual Obligation, Due in Fourth Year | 0 |
Contractual Obligation, Due in Fifth Year | 0 |
Contractual Obligation, Due after Fifth Year | 0 |
Commonwealth Edison Co [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 214 |
Contractual Obligation, Due in Next Fiscal Year | 12 |
Contractual Obligation, Due in Second Year | 0 |
Contractual Obligation, Due in Third Year | 2 |
Contractual Obligation, Due in Fourth Year | 0 |
Contractual Obligation, Due in Fifth Year | 0 |
Contractual Obligation, Due after Fifth Year | 200 |
PECO Energy Co [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 187 |
Contractual Obligation, Due in Next Fiscal Year | 9 |
Contractual Obligation, Due in Second Year | 0 |
Contractual Obligation, Due in Third Year | 0 |
Contractual Obligation, Due in Fourth Year | 0 |
Contractual Obligation, Due in Fifth Year | 0 |
Contractual Obligation, Due after Fifth Year | 178 |
Baltimore Gas and Electric Company [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 20 |
Contractual Obligation, Due in Next Fiscal Year | 5 |
Contractual Obligation, Due in Second Year | 15 |
Contractual Obligation, Due in Third Year | 0 |
Contractual Obligation, Due in Fourth Year | 0 |
Contractual Obligation, Due in Fifth Year | 0 |
Contractual Obligation, Due after Fifth Year | 0 |
Pepco Holdings LLC [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 73 |
Contractual Obligation, Due in Next Fiscal Year | 44 |
Contractual Obligation, Due in Second Year | 11 |
Contractual Obligation, Due in Third Year | 2 |
Contractual Obligation, Due in Fourth Year | 3 |
Contractual Obligation, Due in Fifth Year | 3 |
Contractual Obligation, Due after Fifth Year | 10 |
Potomac Electric Power Company [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 49 |
Contractual Obligation, Due in Next Fiscal Year | 34 |
Contractual Obligation, Due in Second Year | 9 |
Contractual Obligation, Due in Third Year | 1 |
Contractual Obligation, Due in Fourth Year | 1 |
Contractual Obligation, Due in Fifth Year | 1 |
Contractual Obligation, Due after Fifth Year | 3 |
Guarantee obligations maximum exposure | 19 |
Delmarva Power & Light Company [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 15 |
Contractual Obligation, Due in Next Fiscal Year | 6 |
Contractual Obligation, Due in Second Year | 1 |
Contractual Obligation, Due in Third Year | 1 |
Contractual Obligation, Due in Fourth Year | 1 |
Contractual Obligation, Due in Fifth Year | 1 |
Contractual Obligation, Due after Fifth Year | 5 |
Guarantee obligations maximum exposure | 26 |
Atlantic City Electric Company [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 9 |
Contractual Obligation, Due in Next Fiscal Year | 4 |
Contractual Obligation, Due in Second Year | 1 |
Contractual Obligation, Due in Third Year | 0 |
Contractual Obligation, Due in Fourth Year | 1 |
Contractual Obligation, Due in Fifth Year | 1 |
Contractual Obligation, Due after Fifth Year | 2 |
Guarantee obligations maximum exposure | 16 |
Financial Standby Letter of Credit [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 1,703 | [1]
Contractual Obligation, Due in Next Fiscal Year | 1,394 | [1]
Contractual Obligation, Due in Second Year | 308 | [1]
Contractual Obligation, Due in Third Year | 1 | [1]
Contractual Obligation, Due in Fourth Year | 0 | [1]
Contractual Obligation, Due in Fifth Year | 0 | [1]
Contractual Obligation, Due after Fifth Year | 0 | [1]
Financial Standby Letter of Credit [Member] | Exelon Generation Co L L C [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 1,680 | [2]
Contractual Obligation, Due in Next Fiscal Year | 1,380 | [2]
Contractual Obligation, Due in Second Year | 299 | [2]
Contractual Obligation, Due in Third Year | 1 | [2]
Contractual Obligation, Due in Fourth Year | 0 | [2]
Contractual Obligation, Due in Fifth Year | 0 | [2]
Contractual Obligation, Due after Fifth Year | 0 | [2]
Financial Standby Letter of Credit [Member] | Commonwealth Edison Co [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 2 | [3]
Contractual Obligation, Due in Next Fiscal Year | 2 | [3]
Contractual Obligation, Due in Second Year | 0 | [3]
Contractual Obligation, Due in Third Year | 0 | [3]
Contractual Obligation, Due in Fourth Year | 0 | [3]
Contractual Obligation, Due in Fifth Year | 0 | [3]
Contractual Obligation, Due after Fifth Year | 0 | [3]
Financial Standby Letter of Credit [Member] | Baltimore Gas and Electric Company [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 3 | [4]
Contractual Obligation, Due in Next Fiscal Year | 2 | [4]
Contractual Obligation, Due in Second Year | 1 | [4]
Contractual Obligation, Due in Third Year | 0 | [4]
Contractual Obligation, Due in Fourth Year | 0 | [4]
Contractual Obligation, Due in Fifth Year | 0 | [4]
Contractual Obligation, Due after Fifth Year | 0 | [4]
Financial Standby Letter of Credit [Member] | Pepco Holdings LLC [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 8 |
Contractual Obligation, Due in Next Fiscal Year | 0 |
Contractual Obligation, Due in Second Year | 8 |
Contractual Obligation, Due in Third Year | 0 |
Contractual Obligation, Due in Fourth Year | 0 |
Contractual Obligation, Due in Fifth Year | 0 |
Contractual Obligation, Due after Fifth Year | 0 |
Financial Standby Letter of Credit [Member] | Potomac Electric Power Company [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 8 |
Contractual Obligation, Due in Next Fiscal Year | 0 |
Contractual Obligation, Due in Second Year | 8 |
Contractual Obligation, Due in Third Year | 0 |
Contractual Obligation, Due in Fourth Year | 0 |
Contractual Obligation, Due in Fifth Year | 0 |
Contractual Obligation, Due after Fifth Year | 0 |
Surety Bond [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 1,402 | [5]
Contractual Obligation, Due in Next Fiscal Year | 1,331 | [5]
Contractual Obligation, Due in Second Year | 33 | [5]
Contractual Obligation, Due in Third Year | 38 | [5]
Contractual Obligation, Due in Fourth Year | 0 | [5]
Contractual Obligation, Due in Fifth Year | 0 | [5]
Contractual Obligation, Due after Fifth Year | 0 | [5]
Surety Bond [Member] | Exelon Generation Co L L C [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 1,220 |
Contractual Obligation, Due in Next Fiscal Year | 1,201 |
Contractual Obligation, Due in Second Year | 19 |
Contractual Obligation, Due in Third Year | 0 |
Contractual Obligation, Due in Fourth Year | 0 |
Contractual Obligation, Due in Fifth Year | 0 |
Contractual Obligation, Due after Fifth Year | 0 |
Surety Bond [Member] | Commonwealth Edison Co [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 12 | [6]
Contractual Obligation, Due in Next Fiscal Year | 10 | [6]
Contractual Obligation, Due in Second Year | 0 | [6]
Contractual Obligation, Due in Third Year | 2 | [6]
Contractual Obligation, Due in Fourth Year | 0 | [6]
Contractual Obligation, Due in Fifth Year | 0 | [6]
Contractual Obligation, Due after Fifth Year | 0 | [6]
Surety Bond [Member] | PECO Energy Co [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 9 | [7]
Contractual Obligation, Due in Next Fiscal Year | 9 | [7]
Contractual Obligation, Due in Second Year | 0 | [7]
Contractual Obligation, Due in Third Year | 0 | [7]
Contractual Obligation, Due in Fourth Year | 0 | [7]
Contractual Obligation, Due in Fifth Year | 0 | [7]
Contractual Obligation, Due after Fifth Year | 0 | [7]
Surety Bond [Member] | Baltimore Gas and Electric Company [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 17 | [8]
Contractual Obligation, Due in Next Fiscal Year | 3 | [8]
Contractual Obligation, Due in Second Year | 14 | [8]
Contractual Obligation, Due in Third Year | 0 | [8]
Contractual Obligation, Due in Fourth Year | 0 | [8]
Contractual Obligation, Due in Fifth Year | 0 | [8]
Contractual Obligation, Due after Fifth Year | 0 | [8]
Surety Bond [Member] | Pepco Holdings LLC [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 41 |
Contractual Obligation, Due in Next Fiscal Year | 41 |
Contractual Obligation, Due in Second Year | 0 |
Contractual Obligation, Due in Third Year | 0 |
Contractual Obligation, Due in Fourth Year | 0 |
Contractual Obligation, Due in Fifth Year | 0 |
Contractual Obligation, Due after Fifth Year | 0 |
Surety Bond [Member] | Potomac Electric Power Company [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 33 | [9]
Contractual Obligation, Due in Next Fiscal Year | 33 | [9]
Contractual Obligation, Due in Second Year | 0 | [9]
Contractual Obligation, Due in Third Year | 0 | [9]
Contractual Obligation, Due in Fourth Year | 0 | [9]
Contractual Obligation, Due in Fifth Year | 0 | [9]
Contractual Obligation, Due after Fifth Year | 0 | [9]
Surety Bond [Member] | Delmarva Power & Light Company [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 5 | [10]
Contractual Obligation, Due in Next Fiscal Year | 5 | [10]
Contractual Obligation, Due in Second Year | 0 | [10]
Contractual Obligation, Due in Third Year | 0 | [10]
Contractual Obligation, Due in Fourth Year | 0 | [10]
Contractual Obligation, Due in Fifth Year | 0 | [10]
Contractual Obligation, Due after Fifth Year | 0 | [10]
Surety Bond [Member] | Atlantic City Electric Company [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 3 |
Contractual Obligation, Due in Next Fiscal Year | 3 |
Contractual Obligation, Due in Second Year | 0 |
Contractual Obligation, Due in Third Year | 0 |
Contractual Obligation, Due in Fourth Year | 0 |
Contractual Obligation, Due in Fifth Year | 0 |
Contractual Obligation, Due after Fifth Year | 0 |
Trust Preferred Securities [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 378 |
Contractual Obligation, Due in Next Fiscal Year | 0 |
Contractual Obligation, Due in Second Year | 0 |
Contractual Obligation, Due in Third Year | 0 |
Contractual Obligation, Due in Fourth Year | 0 |
Contractual Obligation, Due in Fifth Year | 0 |
Contractual Obligation, Due after Fifth Year | 378 |
Trust Preferred Securities [Member] | Commonwealth Edison Co [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 200 |
Contractual Obligation, Due in Next Fiscal Year | 0 |
Contractual Obligation, Due in Second Year | 0 |
Contractual Obligation, Due in Third Year | 0 |
Contractual Obligation, Due in Fourth Year | 0 |
Contractual Obligation, Due in Fifth Year | 0 |
Contractual Obligation, Due after Fifth Year | 200 |
Trust Preferred Securities [Member] | PECO Energy Co [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 178 |
Contractual Obligation, Due in Next Fiscal Year | 0 |
Contractual Obligation, Due in Second Year | 0 |
Contractual Obligation, Due in Third Year | 0 |
Contractual Obligation, Due in Fourth Year | 0 |
Contractual Obligation, Due in Fifth Year | 0 |
Contractual Obligation, Due after Fifth Year | 178 |
GuaranteedLeaseResidualValues [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 24 | [11]
Contractual Obligation, Due in Next Fiscal Year | 3 | [11]
Contractual Obligation, Due in Second Year | 3 | [11]
Contractual Obligation, Due in Third Year | 2 | [11]
Contractual Obligation, Due in Fourth Year | 3 | [11]
Contractual Obligation, Due in Fifth Year | 3 | [11]
Contractual Obligation, Due after Fifth Year | 10 | [11]
GuaranteedLeaseResidualValues [Member] | Pepco Holdings LLC [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 24 | [12]
Contractual Obligation, Due in Next Fiscal Year | 3 | [12]
Contractual Obligation, Due in Second Year | 3 | [12]
Contractual Obligation, Due in Third Year | 2 | [12]
Contractual Obligation, Due in Fourth Year | 3 | [12]
Contractual Obligation, Due in Fifth Year | 3 | [12]
Contractual Obligation, Due after Fifth Year | 10 | [12]
GuaranteedLeaseResidualValues [Member] | Potomac Electric Power Company [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 8 | [13]
Contractual Obligation, Due in Next Fiscal Year | 1 | [13]
Contractual Obligation, Due in Second Year | 1 | [13]
Contractual Obligation, Due in Third Year | 1 | [13]
Contractual Obligation, Due in Fourth Year | 1 | [13]
Contractual Obligation, Due in Fifth Year | 1 | [13]
Contractual Obligation, Due after Fifth Year | 3 | [13]
GuaranteedLeaseResidualValues [Member] | Delmarva Power & Light Company [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 10 | [14]
Contractual Obligation, Due in Next Fiscal Year | 1 | [14]
Contractual Obligation, Due in Second Year | 1 | [14]
Contractual Obligation, Due in Third Year | 1 | [14]
Contractual Obligation, Due in Fourth Year | 1 | [14]
Contractual Obligation, Due in Fifth Year | 1 | [14]
Contractual Obligation, Due after Fifth Year | 5 | [14]
GuaranteedLeaseResidualValues [Member] | Atlantic City Electric Company [Member] |  |
Guarantor Obligations [Line Items] |  |
Contractual Obligation | 6 | [15]
Contractual Obligation, Due in Next Fiscal Year | 1 | [15]
Contractual Obligation, Due in Second Year | 1 | [15]
Contractual Obligation, Due in Third Year | 0 | [15]
Contractual Obligation, Due in Fourth Year | 1 | [15]
Contractual Obligation, Due in Fifth Year | 1 | [15]
Contractual Obligation, Due after Fifth Year | $ 2 | [15]
[1] | _
[2] | _
[3] | _
[4] | _
[5] | Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds.
[6] | Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bond
[7] | )Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bond
[8] | Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bond
[9] | (a)Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bond
[10] | )Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bond
[11] | Represents the maximum potential obligation in the event that the fair value of certain leased equipment and fleet vehicles is zero at the end of the maximum lease term. The maximum lease term associated with these assets ranges from 3 to 8 years. The maximum potential obligation at the end of the minimum lease term would be $61 million, $19 million of which is a guarantee by Pepco, $26 million by DPL and $16 million by ACE. The minimum lease term associated with these assets ranges from 1 to 4 years. Historically, payments under the guarantees have not been made and PHI believes the likelihood of payments being required under the guarantees is remote.
[12] | (a)Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds.(b)Represents the maximum potential obligation in the event that the fair value of certain leased equipment and fleet vehicles is zero at the end of the maximum lease term. The maximum lease term associated with these assets ranges from 3 to 8 years. The maximum potential obligation at the end of the minimum lease term would be $61 million. The minimum lease term associated with these assets ranges from 1 to 4 years. Historically, payments under the guarantees have not been made and PHI believes the likelihood of payments being required under the guarantees is remot
[13] | Represents the maximum potential obligation in the event that the fair value of certain leased equipment and fleet vehicles is zero at the end of the maximum lease term. The maximum lease term associated with these assets ranges from 3 to 8 years. The maximum potential obligation at the end of the minimum lease term would be $19 million. The minimum lease term associated with these assets ranges from 1 to 4 years. Historically, payments under the guarantees have not been made and Pepco believes the likelihood of payments being required under the guarantees is remot
[14] | )Represents the maximum potential obligation in the event that the fair value of certain leased equipment and fleet vehicles is zero at the end of the maximum lease term. The maximum lease term associated with these assets ranges from 3 to 8 years. The maximum potential obligation at the end of the minimum lease term would be $26 million. The minimum lease term associated with these assets ranges from 1 to 4 years. Historically, payments under the guarantees have not been made and DPL believes the likelihood of payments being required under the guarantees is remot
[15] | )Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds.(b)Represents the maximum potential obligation in the event that the fair value of certain leased equipment and fleet vehicles is zero at the end of the maximum lease term. The maximum lease term associated with these assets ranges from 3 to 8 years. The maximum potential obligation at the end of the minimum lease term would be $16 million. The minimum lease term associated with these assets ranges from 1 to 4 years. Historically, payments under the guarantees have not been made and ACE believes the likelihood of payments being required under the guarantees is remot

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