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Derivative Instruments and Hedging Activities (Narrative) (Details) - USD ($) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2022 | Sep. 30, 2021 | Sep. 30, 2022 | Sep. 30, 2021 | Dec. 31, 2021
Derivative [Line Items] |  |  |  |  |
Net unrealized gains (losses) arising during the period | $ (111,549,000) | $ (8,081,000) | $ (284,216,000) | $ (39,061,000) |
Unrealized gain, after tax | (84,967,000) | (6,037,000) | (216,531,000) | (28,657,000) |
Income recognized | 690,000 | 4,000,000 | 3,900,000 | 9,300,000 |
Cash flow hedge gain (loss) to be reclassified |  |  | (138,000,000) |  |
Cash flow hedge termination gain |  |  | 1,000,000 |  |
Collateral requirements | 58,600,000 |  | 58,600,000 |  | $ 64,500,000
Cash Flow Hedges |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Net unrealized gains (losses) arising during the period | 0 | 488,000 | 0 | 1,200,000 |
Unrealized gain, after tax |  | $ 364,000 |  | $ 930,000 |
Cash Flow Hedges | Forward-Starting Cash Flow Hedges Added In Q3 QTD 2022 |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Increase in derivative, notional amount | 0 |  |  |  |
Cash Flow Hedges | Forward-Starting Cash Flow Hedges Added In Q3 YTD 2022 |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Increase in derivative, notional amount |  |  | 1,650,000,000 |  |
Fair Value Hedges | Interest rate contracts |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Increase in derivative, notional amount | $ 947,100,000 |  | $ 1,770,000,000 |  |

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