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Derivative Instruments and Hedging Activities (Narrative) (Details) - USD ($) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022 | Dec. 31, 2022
Derivative [Line Items] |  |  |  |  |
Net unrealized gains (losses) arising during the period | $ (39,096,000) | $ (111,549,000) | $ (102,218,000) | $ (284,216,000) |
(Loss) income recognized | (6,200,000) | 690,000 | (17,700,000) | 3,900,000 |
Cash flow hedge loss to be reclassified |  |  | 155,000,000 |  |
Cash flow hedge termination loss |  |  | 22,000,000 |  |
Right to reclaim cash collateral | 77,500,000 |  | 77,500,000 |  | $ 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 |
Fair Value Hedges | Interest Rate Contract | Long-term debt |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Hedged liability, discontinued fair value hedge | 347,600,000 |  |  |  |
Fair Value Hedges | Interest Rate Contract | Interest-bearing deposits |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Hedged liability, discontinued fair value hedge | $ 150,000,000 |  |  |  |

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