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Derivative Instruments and Hedging Activities (Narrative) (Details) - USD ($) | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2023 | Jun. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022 | Dec. 31, 2022
Derivative [Line Items] |  |  |  |  |
Net unrealized gains (losses) arising during the period | $ (73,123,000) | $ (48,332,000) | $ (63,123,000) | $ (184,310,000) |
Income (loss) recognized | (6,100,000) | 1,000,000 | (11,500,000) | 3,200,000 |
Cash flow hedge gain (loss) to be reclassified |  |  | (161,000,000) |  |
Cash flow hedge termination gain |  |  | 23,000,000 |  |
Right to reclaim cash collateral | 87,500,000 |  | 87,500,000 |  | $ 66,800,000
Obligation to return cash collateral | 5,700,000 |  | 5,700,000 |  | $ 7,700,000
Cash Flow Hedges |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Net unrealized gains (losses) arising during the period | $ 0 | $ 0 | $ 0 | $ 0 |

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