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Severance Severance - Liabilities Rollforward (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Restructuring Cost and Reserve [Line Items] |  |  |
Restructuring Reserve | $ 77 | $ 94 | $ 88
Payments for Restructuring |  | (29) |
Severance [Member] |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Severance Costs | 35 | 35 |
Payments for Restructuring | (52) |  |
Exelon Generation Co L L C [Member] |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Restructuring Reserve | 47 | 58 | 36
Payments for Restructuring |  | (9) |
Exelon Generation Co L L C [Member] | Severance [Member] |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Severance Costs | 9 | 31 |
Payments for Restructuring | (20) |  |
Commonwealth Edison Co [Member] |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Restructuring Reserve | 2 | 3 | 3
Payments for Restructuring |  | (2) |
Commonwealth Edison Co [Member] | Severance [Member] |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Severance Costs | 1 | 2 |
Payments for Restructuring | (2) |  |
PECO Energy Co [Member] |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Restructuring Reserve | 0 | 0 | 0
Payments for Restructuring |  | 0 |
PECO Energy Co [Member] | Severance [Member] |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Severance Costs | 0 | 0 |
Payments for Restructuring | 0 |  |
Baltimore Gas and Electric Company [Member] |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Restructuring Reserve | 1 | 0 | 0
Payments for Restructuring |  | 0 |
Baltimore Gas and Electric Company [Member] | Severance [Member] |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Severance Costs | 1 | 0 |
Payments for Restructuring | 0 |  |
Pepco Holdings LLC [Member] | Successor [Member] |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Restructuring Reserve | 7 | 20 | 29
Payments for Restructuring |  | (12) |
Pepco Holdings LLC [Member] | Successor [Member] | Severance [Member] |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Severance Costs | 5 | 3 |
Payments for Restructuring | (18) |  |
Potomac Electric Power Company [Member] |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Restructuring Reserve | 0 | 0 | 0
Payments for Restructuring |  | 0 |
Potomac Electric Power Company [Member] | Severance [Member] |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Severance Costs | 1 | 0 |
Payments for Restructuring | (1) |  |
Delmarva Power & Light Company [Member] |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Restructuring Reserve | 0 | 0 | 0
Payments for Restructuring |  | 0 |
Delmarva Power & Light Company [Member] | Severance [Member] |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Severance Costs | 0 | 0 |
Payments for Restructuring | 0 |  |
Atlantic City Electric Company [Member] |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Restructuring Reserve | 0 | 0 | $ 0
Payments for Restructuring |  | 0 |
Atlantic City Electric Company [Member] | Severance [Member] |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Severance Costs | 0 | $ 0 |
Payments for Restructuring | $ 0 |  |

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- Definition Amount of cash payments made as the result of exit or disposal activities. Excludes payments associated with a discontinued operation or an asset retirement obligation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3536-108585 + Details
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- Definition Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB TOPIC 5.P.4(b)) -URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869 + Details
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- Definition Amount of expenses for special or contractual termination benefits provided to current employees involuntarily terminated under a benefit arrangement associated exit or disposal activities pursuant to an authorized plan. Excludes expenses related to one-time termination benefits, a discontinued operation or an asset retirement obligation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB Topic 5.P.4(b)) -URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 5.P.3) -URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140864-122747 + Details
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