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Material Contingencies - Con Edison Transmission (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019
Guarantor Obligations [Line Items] |  |
Guarantee obligations maximum exposure | $ 2,042 | $ 1,831
Payment Guarantee by CET Electric of Contributions to New York Transco LLC |  |
Guarantor Obligations [Line Items] |  |
Estimated project cost percentage | 175.00% |
NY Transco | Payment Guarantee by CET Electric of Contributions to New York Transco LLC |  |
Guarantor Obligations [Line Items] |  |
Ownership interest, percentage | 45.70% |

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