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Related Party Transactions - Related Party Transactions included in Consolidated Balance Sheet (Details) - USD ($) | Dec. 31, 2018 | Dec. 31, 2017
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Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current |  | $ 5,000,000 | $ 5,000,000
Long-term debt to financing trusts |  | 390,000,000 | 389,000,000
ComEd Financing III Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current |  | 4,000,000 | 4,000,000
Long-term debt to financing trusts |  | 206,000,000 | 205,000,000
PECO Trust III Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current |  | 1,000,000 | 1,000,000
Long-term debt to financing trusts |  | 81,000,000 | 81,000,000
PECO Trust IV Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Long-term debt to financing trusts |  | 103,000,000 | 103,000,000
Exelon Generation Co L L C [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current |  | 173,000,000 | 140,000,000
Borrowings from Exelon intercompany money pool |  | 100,000,000 | 54,000,000
Payables to affiliates, current |  | 139,000,000 | 123,000,000
Long-term debt due to affiliates |  | 898,000,000 | 910,000,000
Payables to affiliates, noncurrent |  | 2,606,000,000 | 3,065,000,000
Exelon Generation Co L L C [Member] | PECO Energy Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current | [1] | 30,000,000 | 26,000,000
Payables to affiliates, current | [1] | 0 | 4,000,000
Payables to affiliates, noncurrent | [2] | 389,000,000 | 537,000,000
Exelon Generation Co L L C [Member] | Commonwealth Edison Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current | [3] | 69,000,000 | 28,000,000
Payables to affiliates, current |  | 19,000,000 | 12,000,000
Due to Related Parties, Current | [3] | 14,000,000 | 0
Payables to affiliates, noncurrent | [2] | 2,217,000,000 | 2,528,000,000
Exelon Generation Co L L C [Member] | Delmarva Power & Light Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current | [4] | 7,000,000 | 12,000,000
Exelon Generation Co L L C [Member] | Potomac Electric Power Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current | [5] | 28,000,000 | 36,000,000
Exelon Generation Co L L C [Member] | Atlantic City Electric Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current | [6] | 5,000,000 | 6,000,000
Exelon Generation Co L L C [Member] | Baltimore Gas And Electric Company Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current | [7] | 24,000,000 | 24,000,000
Exelon Generation Co L L C [Member] | PHI Service Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current | [8] | 0 | 1,000,000
Exelon Generation Co L L C [Member] | Potomac Capital Investment Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Borrowings from Exelon intercompany money pool |  | 0 | 54,000,000
Exelon Generation Co L L C [Member] | Other Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current |  | 10,000,000 | 7,000,000
Payables to affiliates, current |  | 8,000,000 | 12,000,000
Exelon Generation Co L L C [Member] | Exelon Corporation Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Borrowings from Exelon intercompany money pool |  | 100,000,000 | 0
Payables to affiliates, current | [9] | 17,000,000 | 21,000,000
Long-term debt due to affiliates | [10] | 898,000,000 | 910,000,000
Exelon Generation Co L L C [Member] | Exelon Business Services Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current | [8] | 95,000,000 | 74,000,000
Commonwealth Edison Co [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current |  | 20,000,000 | 13,000,000
Receivable from affiliates, noncurrent |  | 2,217,000,000 | 2,528,000,000
Payables to affiliates, current |  | 119,000,000 | 74,000,000
Long-term debt to financing trusts |  | 205,000,000 | 205,000,000
Commonwealth Edison Co [Member] | Exelon Generation Co LLC Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current |  | 19,000,000 | 12,000,000
Receivable from affiliates, noncurrent | [11] | 2,217,000,000 | 2,528,000,000
Payables to affiliates, current | [12] | 55,000,000 | 28,000,000
Commonwealth Edison Co [Member] | ComEd Financing III Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current |  | 4,000,000 | 4,000,000
Long-term debt to financing trusts |  | 205,000,000 | 205,000,000
Commonwealth Edison Co [Member] | Voluntary Employee Beneficiary Association Trust Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Prepaid voluntary employee beneficiary association trust | [13] | 5,000,000 | 2,000,000
Receivables from affiliates, current |  | 1,000,000 | 1,000,000
Commonwealth Edison Co [Member] | Exelon Corporation Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current |  | 4,000,000 | 3,000,000
Commonwealth Edison Co [Member] | Exelon Business Services Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current | [14] | 56,000,000 | 39,000,000
PECO Energy Co [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivable from affiliates, noncurrent |  | 389,000,000 | 537,000,000
Payables to affiliates, current |  | 59,000,000 | 53,000,000
Long-term debt to financing trusts | [15] | 184,000,000 | 184,000,000
PECO Energy Co [Member] | Exelon Generation Co LLC Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivable from affiliates, noncurrent | [16] | 389,000,000 | 537,000,000
Payables to affiliates, current | [17] | 30,000,000 | 22,000,000
PECO Energy Co [Member] | PECO Trust III Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current |  | 1,000,000 | 1,000,000
Long-term debt to financing trusts |  | 81,000,000 | 81,000,000
PECO Energy Co [Member] | PECO Trust IV Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Long-term debt to financing trusts |  | 103,000,000 | 103,000,000
PECO Energy Co [Member] | Voluntary Employee Beneficiary Association Trust Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Prepaid voluntary employee beneficiary association trust | [18] | 1,000,000 | 0
PECO Energy Co [Member] | Exelon Corporation Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current |  | 2,000,000 | 1,000,000
PECO Energy Co [Member] | Exelon Business Services Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current | [19] | 26,000,000 | 29,000,000
Baltimore Gas and Electric Company [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current |  | 1,000,000 | 1,000,000
Payables to affiliates, current |  | 65,000,000 | 52,000,000
Baltimore Gas and Electric Company [Member] | Exelon Generation Co LLC Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current | [20] | 24,000,000 | 24,000,000
Baltimore Gas and Electric Company [Member] | Other Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current |  | 1,000,000 | 1,000,000
Payables to affiliates, current |  | 1,000,000 | 2,000,000
Baltimore Gas and Electric Company [Member] | Exelon Corporation Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current |  | 2,000,000 | 1,000,000
Baltimore Gas and Electric Company [Member] | Exelon Business Services Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current | [21] | 38,000,000 | 25,000,000
Pepco Holdings LLC [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current |  | 94,000,000 | 90,000,000
Pepco Holdings LLC [Member] | Exelon Generation Co LLC Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current |  | 40,000,000 | 54,000,000
Pepco Holdings LLC [Member] | Baltimore Gas And Electric Company Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current |  | 0 | 1,000,000
Pepco Holdings LLC [Member] | Other Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current |  | 7,000,000 | 5,000,000
Pepco Holdings LLC [Member] | Exelon Corporation Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current |  | 6,000,000 | 6,000,000
Pepco Holdings LLC [Member] | Exelon Business Services Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current | [22] | 41,000,000 | 24,000,000
Potomac Electric Power Company [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current |  | 1,000,000 | 0
Payables to affiliates, current |  | 62,000,000 | 74,000,000
Potomac Electric Power Company [Member] | Exelon Generation Co LLC Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current | [23] | 28,000,000 | 36,000,000
Potomac Electric Power Company [Member] | Delmarva Power & Light Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current |  | 1,000,000 | 0
Potomac Electric Power Company [Member] | PHI Service Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current | [24] | 14,000,000 | 27,000,000
Potomac Electric Power Company [Member] | Exelon Corporation Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current |  | 1,000,000 | 0
Potomac Electric Power Company [Member] | Exelon Business Services Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current | [24] | 19,000,000 | 11,000,000
Delmarva Power & Light Company [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current |  | 33,000,000 | 46,000,000
Delmarva Power & Light Company [Member] | Exelon Generation Co LLC Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current | [25] | 7,000,000 | 12,000,000
Delmarva Power & Light Company [Member] | Potomac Electric Power Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current |  | 1,000,000 | 0
Delmarva Power & Light Company [Member] | Atlantic City Electric Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current |  | 1,000,000 | 0
Delmarva Power & Light Company [Member] | PHI Service Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current | [26] | 12,000,000 | 27,000,000
Delmarva Power & Light Company [Member] | Exelon Corporation Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current |  | 1,000,000 | 0
Delmarva Power & Light Company [Member] | Exelon Business Services Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current | [26] | 11,000,000 | 7,000,000
Atlantic City Electric Company [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current |  | 1,000,000 | 0
Payables to affiliates, current |  | 28,000,000 | 29,000,000
Atlantic City Electric Company [Member] | Delmarva Power & Light Company [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current |  | 1,000,000 | 0
Atlantic City Electric Company [Member] | Exelon Generation Co LLC Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current | [27] | 5,000,000 | 6,000,000
Atlantic City Electric Company [Member] | PHI Service Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current | [28] | 13,000,000 | 18,000,000
Atlantic City Electric Company [Member] | Other Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current |  | 2,000,000 | 0
Atlantic City Electric Company [Member] | Exelon Business Services Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Payables to affiliates, current | [28] | 8,000,000 | 5,000,000
Parent Company [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current |  | 44,000,000 | 33,000,000
Note receivable from affiliates, current |  | 216,000,000 | 217,000,000
Payables to affiliates, current |  | 360,000,000 | 360,000,000
Parent Company [Member] | Exelon Generation Co L L C [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current |  | 17,000,000 | 21,000,000
Note receivable from affiliates, current | [29] | 100,000,000 | 0
Parent Company [Member] | PHI Service Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current |  | 6,000,000 | 6,000,000
Parent Company [Member] | Exelon Business Services Co Affiliate [Member] |  |  |
Related Party Transaction [Line Items] |  |  |
Receivables from affiliates, current | [30] | 13,000,000 | 1,000,000
Note receivable from affiliates, current | [30] | $ 116,000,000 | $ 217,000,000
[1] | Generation provides electric supply to PECO under contracts executed through PECO’s competitive procurement process. In addition, Generation has a ten-year agreement with PECO to sell solar AECs.
[2] | Generation has long-term payables to ComEd and PECO as a result of the nuclear decommissioning contractual construct whereby, to the extent NDT funds are greater than the underlying ARO at the end of decommissioning, such amounts are due back to ComEd and PECO, as applicable, for payment to their respective customers. See Note 15—Asset Retirement Obligations for additional information.
[3] | Generation has an ICC-approved RFP contract with ComEd to provide a portion of ComEd’s electricity supply requirements. Generation also sells RECs and ZECs to ComEd.
[4] | Generation provides a portion of DPL's energy requirements under its MDPSC and DPSC approved market based SOS and gas commodity programs.
[5] | Generation provides electric supply to Pepco under contracts executed through Pepco's competitive procurement process approved by the MDPSC and DCPSC.
[6] | Generation provides electric supply to ACE under contracts executed through ACE's competitive procurement process.
[7] | Generation provides a portion of BGE’s energy requirements under its MDPSC-approved market-based SOS and gas commodity programs.
[8] | Generation receives a variety of corporate support services from BSC and PHISCO, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[9] | The balance consists of interest owed to Exelon Corporation related to the senior unsecured notes, as well as, expense related to certain invoices Exelon Corporation processed on behalf of Generation.
[10] | In connection with the debt obligations assumed by Exelon as part of the Constellation merger, Exelon and subsidiaries of Generation (former Constellation subsidiaries) assumed intercompany loan agreements that mirror the terms and amounts of the third-party debt obligations of Exelon, resulting in intercompany notes payable included in Long-term Debt to affiliates in Generation’s Consolidated Balance Sheets and intercompany notes receivable at Exelon Corporate, which are eliminated in consolidation in Exelon’s Consolidated Balance Sheets.
[11] | ComEd has a long-term receivable from Generation as a result of the nuclear decommissioning contractual construct for generating facilities previously owned by ComEd. To the extent the assets associated with decommissioning are greater than the applicable ARO at the end of decommissioning, such amounts are due back to ComEd for payment to ComEd’s customers.
[12] | ComEd procures a portion of its electricity supply requirements from Generation under an ICC-approved RFP contract. ComEd also purchases RECs and ZECs from Generation.
[13] | The voluntary employee benefit association trusts covering active employees are included in corporate operations and are funded by the Registrants. A prepayment to the active welfare plans has accumulated due to actuarially determined contribution rates, which are the basis for ComEd’s contributions to the plans, being higher than actual claim expense incurred by the plans over time. The prepayment is included in other current assets.
[14] | ComEd receives a variety of corporate support services from BSC, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[15] | Amounts owed to this financing trust are recorded as Long-term debt to financing trusts within PECO’s Consolidated Balance Sheets.
[16] | PECO has a long-term receivable from Generation as a result of the nuclear decommissioning contractual construct, whereby, to the extent the assets associated with decommissioning are greater than the applicable ARO at the end of decommissioning, such amounts are due back to PECO for payment to PECO’s customers.
[17] | PECO purchases electric supply from Generation under contracts executed through its competitive procurement process. In addition, PECO has five-year and ten-year agreements with Generation to purchase non-solar and solar AECs, respectively.
[18] | The voluntary employee beneficiary association trusts covering active employees are included in corporate operations and are funded by the Registrants. A prepayment to the active welfare plans has accumulated due to actuarially determined contribution rates, which are the basis for PECO’s contributions to the plans, being higher than actual claim expense incurred by the plans over time.
[19] | PECO receives a variety of corporate support services from BSC, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[20] | BGE procures a portion of its electricity and gas supply requirements from Generation under its MDPSC-approved market-based SOS and gas commodity programs.
[21] | BGE receives a variety of corporate support services from BSC, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[22] | PHI receives a variety of corporate support services from BSC and PHISCO, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[23] | Pepco procures a portion of its electricity supply requirements from Generation under its MDPSC and DCPSC approved market based SOS commodity programs.
[24] | Pepco receives a variety of corporate support services from BSC and PHISCO, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[25] | DPL procures a portion of its electricity and gas supply requirements from Generation under its MDPSC and DPSC approved market based SOS and gas commodity programs.
[26] | DPL receives a variety of corporate support services from BSC and PHISCO, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[27] | ACE purchases electric supply from Generation under contracts executed through its competitive procurement process.
[28] | ACE receives a variety of corporate support services from BSC and PHISCO, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[29] | In connection with the debt obligations assumed by Exelon as part of the Constellation merger, Exelon and subsidiaries of Generation (former Constellation subsidiaries) assumed intercompany loan agreements that mirror the terms and amounts of the third-party debt obligations of Exelon, resulting in intercompany notes payable included in Long-Term Debt to affiliates in Generation’s Consolidated Balance Sheets and intercompany notes receivable at Exelon Corporate, which are eliminated in consolidation in Exelon’s Consolidated Balance Sheets.
[30] | Exelon Corporate receives a variety of corporate support services from BSC, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead.

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