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Variable Interest Entities Variable Interest Entities - Assets and Liabilities of VIEs which Creditors or Beneficiaries have No Recourse (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
--- | --- | --- | --- | ---
Variable Interest Entity [Line Items] |  |  |  |  |
Cash and cash equivalents |  | $ 1,349 | $ 898 | $ 635 | $ 6,502
Restricted cash |  | 247 | 207 | 253 | 205
Customer |  | 4,607 | 4,445 |  |
Other |  | 1,256 | 1,132 |  |
Mark-to-market derivative assets, current |  | 804 | 976 |  |
Other current assets |  | 1,238 | 1,260 |  |
Total current assets |  | 13,360 | 11,896 |  |
Property, plant and equipment, net |  | 76,707 | 74,202 |  |
Nuclear decommissioning trust funds |  | 11,661 | 13,272 |  |
Goodwill |  | 6,677 | 6,677 | 6,677 |
Mark-to-market derivative assets, noncurrent |  | 452 | 337 |  |
Other noncurrent assets |  | 1,575 | 1,330 |  |
Total assets | [1] | 119,666 | 116,770 |  |
Long-term debt due within one year |  | 1,349 | 2,088 |  |
Accounts payable |  | 3,800 | 3,532 |  |
Accrued expenses |  | 2,112 | 1,837 |  |
Mark-to-market derivative liabilities, current |  | 475 | 232 |  |
Unamortized energy contract liabilities |  | 149 | 231 |  |
Other current liabilities |  | 1,035 | 1,069 |  |
Total current liabilities |  | 11,404 | 10,798 |  |
Long-term debt |  | 34,075 | 32,176 |  |
Asset retirement obligations |  | 9,679 | 10,029 |  |
Pension obligations |  | 3,988 | 3,736 |  |
Unamortized energy contract liabilities |  | 463 | 609 |  |
Other noncurrent liabilities |  | 2,130 | 2,097 |  |
Total liabilities | [1] | 86,596 | 84,583 |  |
Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |
Cash and cash equivalents | [2] | 414 | 126 |  |
Restricted cash | [2] | 66 | 64 |  |
Customer | [2] | 146 | 170 |  |
Other | [2] | 23 | 25 |  |
Materials and supplies | [2] | 212 | 205 |  |
Other current assets | [2] | 52 | 45 |  |
Total current assets | [2] | 913 | 635 |  |
Property, plant and equipment, net | [2] | 6,145 | 6,186 |  |
Nuclear decommissioning trust funds | [2] | 2,351 | 2,502 |  |
Other noncurrent assets | [2] | 258 | 274 |  |
Total noncurrent assets | [2] | 8,754 | 8,962 |  |
Total assets | [2] | 9,667 | 9,597 |  |
Long-term debt due within one year | [2] | 87 | 102 |  |
Accounts payable | [2] | 96 | 114 |  |
Accrued expenses | [2] | 72 | 67 |  |
Unamortized energy contract liabilities | [2] | 15 | 18 |  |
Other current liabilities | [2] | 3 | 7 |  |
Total current liabilities | [2] | 273 | 308 |  |
Long-term debt | [2] | 1,072 | 1,154 |  |
Asset retirement obligations | [2] | 2,160 | 2,035 |  |
Unamortized energy contract liabilities |  | 1 |  |  |
Other noncurrent liabilities | [2] | 42 | 121 |  |
Total noncurrent liabilities | [2] | 3,275 | 3,310 |  |
Total liabilities | [2] | 3,548 | 3,618 |  |
Exelon Generation Co L L C [Member] |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |
Cash and cash equivalents |  | 750 | 416 | 290 | 431
Restricted cash |  | 153 | 138 | 158 | 123
Customer |  | 2,941 | 2,697 |  |
Other |  | 562 | 321 |  |
Mark-to-market derivative assets, current |  | 804 | 976 |  |
Other current assets |  | 883 | 933 |  |
Total current assets |  | 8,433 | 6,882 |  |
Property, plant and equipment, net |  | 23,981 | 24,906 |  |
Nuclear decommissioning trust funds |  | 11,661 | 13,272 |  |
Goodwill |  | 47 | 47 |  |
Mark-to-market derivative assets, noncurrent |  | 452 | 334 |  |
Other noncurrent assets |  | 755 | 670 |  |
Total assets | [3] | 47,556 | 48,457 |  |
Long-term debt due within one year |  | 906 | 346 |  |
Accounts payable |  | 1,847 | 1,773 |  |
Accrued expenses |  | 898 | 1,022 |  |
Mark-to-market derivative liabilities, current |  | 449 | 211 |  |
Unamortized energy contract liabilities |  | 31 | 43 |  |
Other current liabilities |  | 279 | 265 |  |
Total current liabilities |  | 5,769 | 4,191 |  |
Long-term debt |  | 6,989 | 7,734 |  |
Asset retirement obligations |  | 9,450 | 9,844 |  |
Unamortized energy contract liabilities |  | 20 | 48 |  |
Other noncurrent liabilities |  | 610 | 658 |  |
Total liabilities | [3] | 32,048 | 32,498 |  |
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |
Cash and cash equivalents |  | 414 | 126 |  |
Restricted cash |  | 62 | 58 |  |
Customer |  | 146 | 170 |  |
Other |  | 23 | 25 |  |
Materials and supplies |  | 212 | 205 |  |
Other current assets |  | 49 | 41 |  |
Total current assets |  | 906 | 625 |  |
Property, plant and equipment, net |  | 6,145 | 6,186 |  |
Nuclear decommissioning trust funds |  | 2,351 | 2,502 |  |
Other noncurrent assets |  | 232 | 243 |  |
Total noncurrent assets |  | 8,728 | 8,931 |  |
Total assets |  | 9,634 | 9,556 |  |
Long-term debt due within one year |  | 66 | 67 |  |
Accounts payable |  | 96 | 114 |  |
Accrued expenses |  | 72 | 66 |  |
Unamortized energy contract liabilities |  | 15 | 18 |  |
Other current liabilities |  | 3 | 7 |  |
Total current liabilities |  | 252 | 272 |  |
Long-term debt |  | 1,025 | 1,088 |  |
Asset retirement obligations |  | 2,160 | 2,035 |  |
Unamortized energy contract liabilities |  | 1 |  |  |
Other noncurrent liabilities |  | 42 | 121 |  |
Total noncurrent liabilities |  | 3,228 | 3,244 |  |
Total liabilities |  | 3,480 | 3,516 |  |
Pepco Holdings LLC [Member] |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |
Cash and cash equivalents |  | 124 | 30 |  |
Restricted cash |  | 43 | 42 |  |
Customer |  | 453 | 486 |  |
Other |  | 177 | 206 |  |
Other current assets |  | 75 | 75 |  |
Total current assets |  | 1,533 | 1,551 |  |
Property, plant and equipment, net |  | 13,446 | 12,498 |  |
Goodwill |  | 4,005 | 4,005 | 4,005 |
Other noncurrent assets |  | 60 | 70 |  |
Total assets | [4] | 21,984 | 21,247 |  |
Long-term debt due within one year |  | 125 | 396 |  |
Accounts payable |  | 496 | 348 |  |
Accrued expenses |  | 256 | 261 |  |
Unamortized energy contract liabilities |  | 119 | 188 |  |
Other current liabilities |  | 123 | 123 |  |
Total current liabilities |  | 1,592 | 1,931 |  |
Long-term debt |  | 6,134 | 5,478 |  |
Asset retirement obligations |  | 52 | 16 |  |
Unamortized energy contract liabilities |  | 442 | 561 |  |
Other noncurrent liabilities |  | 369 | 389 |  |
Total liabilities | [4] | 12,702 | 12,422 |  |
Pepco Holdings LLC [Member] | Successor [Member] |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |
Cash and cash equivalents |  |  |  | 170 |
Restricted cash |  |  |  | 43 |
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |
Cash and cash equivalents | [2] | 0 | 0 |  |
Restricted cash | [2] | 4 | 6 |  |
Customer | [2] | 0 | 0 |  |
Other | [2] | 0 | 0 |  |
Materials and supplies | [2] | 0 | 0 |  |
Other current assets | [2] | 3 | 4 |  |
Total current assets | [2] | 7 | 10 |  |
Property, plant and equipment, net | [2] | 0 | 0 |  |
Nuclear decommissioning trust funds | [2] | 0 | 0 |  |
Other noncurrent assets | [2] | 26 | 31 |  |
Total noncurrent assets | [2] | 26 | 31 |  |
Total assets | [2] | 33 | 41 |  |
Long-term debt due within one year | [2] | 21 | 35 |  |
Accounts payable | [2] | 0 | 0 |  |
Accrued expenses | [2] | 1 | 1 |  |
Unamortized energy contract liabilities | [2] | 0 | 0 |  |
Other current liabilities | [2] | 0 | 0 |  |
Total current liabilities | [2] | 22 | 36 |  |
Long-term debt | [2] | 47 | 66 |  |
Asset retirement obligations | [2] | 0 | 0 |  |
Unamortized energy contract liabilities |  | 0 |  |  |
Other noncurrent liabilities | [2] | 0 | 0 |  |
Total noncurrent liabilities | [2] | 47 | 66 |  |
Total liabilities | [2] | 69 | 102 |  |
Atlantic City Electric Company [Member] |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |
Cash and cash equivalents |  | 7 | 2 | 101 | 3
Restricted cash |  | 4 | 6 | $ 9 | $ 12
Customer |  | 95 | 92 |  |
Other |  | 55 | 56 |  |
Other current assets |  | 5 | 2 |  |
Total current assets |  | 240 | 258 |  |
Property, plant and equipment, net |  | 2,966 | 2,706 |  |
Other noncurrent assets |  | 40 | 45 |  |
Total assets | [5] | 3,699 | 3,445 |  |
Long-term debt due within one year |  | 18 | 281 |  |
Accounts payable |  | 154 | 118 |  |
Accrued expenses |  | 35 | 33 |  |
Other current liabilities |  | 4 | 8 |  |
Total current liabilities |  | 422 | 619 |  |
Long-term debt |  | 1,170 | 840 |  |
Other noncurrent liabilities |  | 27 | 25 |  |
Total liabilities | [5] | 2,573 | 2,402 |  |
Atlantic City Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |
Cash and cash equivalents |  | 0 | 0 |  |
Restricted cash |  | 4 | 6 |  |
Customer |  | 0 | 0 |  |
Other |  | 0 | 0 |  |
Materials and supplies |  | 0 | 0 |  |
Other current assets |  | 0 | 0 |  |
Total current assets |  | 4 | 6 |  |
Property, plant and equipment, net |  | 0 | 0 |  |
Nuclear decommissioning trust funds |  | 0 | 0 |  |
Other noncurrent assets |  | 19 | 23 |  |
Total noncurrent assets |  | 19 | 23 |  |
Total assets |  | 23 | 29 |  |
Long-term debt due within one year |  | 18 | 31 |  |
Accounts payable |  | 0 | 0 |  |
Accrued expenses |  | 1 | 1 |  |
Unamortized energy contract liabilities |  | 0 | 0 |  |
Other current liabilities |  | 0 | 0 |  |
Total current liabilities |  | 19 | 32 |  |
Long-term debt |  | 40 | 58 |  |
Asset retirement obligations |  | 0 | 0 |  |
Unamortized energy contract liabilities |  | 0 |  |  |
Other noncurrent liabilities |  | 0 | 0 |  |
Total noncurrent liabilities |  | 40 | 58 |  |
Total liabilities |  | $ 59 | $ 90 |  |
[1] | Exelon’s consolidated assets include $9,667 million and $9,597 million at December 31, 2018 and 2017, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,548 million and $3,618 million at December 31, 2018 and 2017, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 2–Variable Interest Entities for additional information.
[2] | Includes certain purchase accounting adjustments not pushed down to the ACE standalone entity.
[3] | Generation’s consolidated assets include $9,634 million and $9,556 million at December 31, 2018 and 2017, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,480 million and $3,516 million at December 31, 2018 and 2017, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 2–Variable Interest Entities for additional information.
[4] | PHI’s consolidated total assets include $33 million and $41 million at December 31, 2018 and 2017, respectively, of PHI's consolidated VIE that can only be used to settle the liabilities of the VIE. PHI’s consolidated total liabilities include $69 million and $102 million at December 31, 2018 and 2017, respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 2 - Variable Interest Entities for additional information.
[5] | ACE’s consolidated assets include $23 million and $29 million at December 31, 2018 and 2017, respectively, of ACE’s consolidated VIE that can only be used to settle the liabilities of the VIE. ACE’s consolidated liabilities include $59 million and $90 million at December 31, 2018 and 2017, respectively, of ACE’s consolidated VIE for which the VIE creditors do not have recourse to ACE. See Note 2 - Variable Interest Entities for additional information.

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