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Environmental Matters - Accrued Liabilities and Regulatory Assets (Details) - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Site Contingency [Line Items] |  |
Accrued Liabilities | $ 734 | $ 779
Regulatory assets | 4,987 | 4,370
Manufactured gas plant sites |  |
Site Contingency [Line Items] |  |
Accrued Liabilities | 640 | 689
Other Superfund Sites |  |
Site Contingency [Line Items] |  |
Accrued Liabilities | 94 | 90
Superfund Sites |  |
Site Contingency [Line Items] |  |
Accrued Liabilities | 734 | 779
Regulatory assets | 732 | 810
CECONY |  |
Site Contingency [Line Items] |  |
Accrued Liabilities | 654 | 693
Regulatory assets | 4,600 | 3,987
CECONY | Manufactured gas plant sites |  |
Site Contingency [Line Items] |  |
Accrued Liabilities | 561 | 603
CECONY | Other Superfund Sites |  |
Site Contingency [Line Items] |  |
Accrued Liabilities | 93 | 90
CECONY | Superfund Sites |  |
Site Contingency [Line Items] |  |
Accrued Liabilities | 654 | 693
Regulatory assets | $ 647 | $ 716

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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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