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Fair Value Measurements - Level 3 Quantitative Information (Details) - Model - Level 3 - FTRs $ in Millions | 6 Months Ended
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Jun. 30, 2021 USD ($) $ / MWh
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |
Fair Value | $ | $ 3
Minimum |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |
Fair Value Inputs, RTO Auction Clearing Prices (in $/MWH) | (0.10)
Maximum |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |
Fair Value Inputs, RTO Auction Clearing Prices (in $/MWH) | 1.90
Weighted Average |
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items] |
Fair Value Inputs, RTO Auction Clearing Prices (in $/MWH) | 0.90

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