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Environmental Matters - Accrued Liability for Asbestos Suits and Workers' Compensation Proceedings (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Site Contingency [Line Items] |  |
Regulatory Liabilities | $ (4,549) | $ (4,929)
Regulatory assets | 6,461 | 4,987
Asbestos Suits |  |
Site Contingency [Line Items] |  |
Accrued liability | 8 | 8
Regulatory assets | 8 | 8
Workers' Compensation |  |
Site Contingency [Line Items] |  |
Accrued liability | 72 | 78
Regulatory Liabilities | (3) |
Regulatory assets |  | 3
CECONY |  |
Site Contingency [Line Items] |  |
Regulatory Liabilities | (4,105) | (4,490)
Regulatory assets | 5,989 | 4,600
CECONY | Asbestos Suits |  |
Site Contingency [Line Items] |  |
Accrued liability | 7 | 7
Regulatory assets | 7 | 7
CECONY | Workers' Compensation |  |
Site Contingency [Line Items] |  |
Accrued liability | 68 | 73
Regulatory Liabilities | $ (3) |
Regulatory assets |  | $ 3

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