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Environmental Matters - Environmental Remediation Costs (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
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Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019
Environmental Exit Cost [Line Items] |  |  |  |
Remediation costs incurred | $ 8 | $ 4 | $ 17 | $ 15
CECONY |  |  |  |
Environmental Exit Cost [Line Items] |  |  |  |
Remediation costs incurred | $ 8 | $ 2 | $ 16 | $ 10

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- Definition The charge against earnings in the period for known or estimated future costs arising from requirements to perform environmental remediation activities. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=109237650&loc=d3e13064-110858 Reference 2: http://www.xbrl.org/2003/role/recommendedDisclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 12 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13296-110859 + Details
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