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Early Plant Retirements Early Plant Retirements - Implications of Potential Early Plant Retirement on Balance Sheet (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Implications of Potential Early Plant Retirement [Line Items] |  |
Property, plant and equipment, net | $ 76,707 | $ 74,202
Exelon Generation Co L L C [Member] |  |
Implications of Potential Early Plant Retirement [Line Items] |  |
Property, plant and equipment, net | 23,981 | $ 24,906
Exelon Generation Co L L C [Member] | Salem [Member] | Facility Closing [Member] |  |
Implications of Potential Early Plant Retirement [Line Items] |  |
Inventory, Raw Materials and Supplies, Gross | 45 |
Nuclear Fuel, Net of Amortization | 118 |
Property, plant and equipment, net | 538 |
Construction in Progress, Gross | 44 |
Asset Retirement Obligation | (395) |
Exelon Generation Co L L C [Member] | Mystic Generating Station [Member] | Facility Closing [Member] |  |
Implications of Potential Early Plant Retirement [Line Items] |  |
Inventory, Raw Materials and Supplies, Gross | 30 |
Nuclear Fuel, Net of Amortization | 20 |
Property, plant and equipment, net | 901 |
Construction in Progress, Gross | 9 |
Asset Retirement Obligation | $ (1) |

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- Definition The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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- Definition Amount of structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 + Details
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- Definition Gross amount of unprocessed materials to be used in manufacturing or production process and supplies that will be consumed. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.6(a)(4),(5)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The carrying amount as of the balance sheet of nuclear fuel held as property plant and equipment. This amount is net of amortization based on the energy produced over the life of the fuel. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.13(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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