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Environmental Matters - Accrued Liabilities and Regulatory Assets (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Site Contingency [Line Items] |  |
Accrued Liabilities | $ 857 | $ 734
Regulatory assets | 6,461 | 4,987
Manufactured gas plant sites |  |
Site Contingency [Line Items] |  |
Accrued Liabilities | 752 | 640
Other Superfund Sites |  |
Site Contingency [Line Items] |  |
Accrued Liabilities | 105 | 94
Superfund Sites |  |
Site Contingency [Line Items] |  |
Accrued Liabilities | 857 | 734
Regulatory assets | 865 | 732
CECONY |  |
Site Contingency [Line Items] |  |
Accrued Liabilities | 780 | 654
Regulatory assets | 5,989 | 4,600
CECONY | Manufactured gas plant sites |  |
Site Contingency [Line Items] |  |
Accrued Liabilities | 676 | 561
CECONY | Other Superfund Sites |  |
Site Contingency [Line Items] |  |
Accrued Liabilities | 104 | 93
CECONY | Superfund Sites |  |
Site Contingency [Line Items] |  |
Accrued Liabilities | 780 | 654
Regulatory assets | $ 791 | $ 647

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- Definition Carrying value of the obligation (known or estimated) arising from requirements to perform activities to remediate one or more sites, payable after twelve months or beyond the next operating cycle if longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.24) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 10 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121557415&loc=d3e14326-108349 + Details
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- Definition The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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