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Comprehensive Income (Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2021 | Jun. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Beginning Balance, December 31, 2020 |  |  | $ 220,186 |
Amounts reclassified from AOCI, HTM related | $ (2) | $ (25) | (4) | $ (5)
Amount reclassified into net income: Net actuarial loss | 548 | 595 | 1,095 | 1,191
Other comprehensive income (loss) | 34,771 | 174,083 | (50,815) | 70,216
Other comprehensive income, defined pension and post retirement plans | 548 | 595 | 1,095 | 1,191
Ending Balance, June 30, 2021 | 169,371 |  | 169,371 |
Available-for-sale Securities [Member] |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Beginning Balance, December 31, 2020 |  |  | 307,790 |
OCI before reclassifications |  |  | (53,527) |
Amounts reclassified from AOCI, All Other |  |  | 523 |
Other comprehensive income (loss) |  |  | (53,004) |
Ending Balance, June 30, 2021 | 254,786 |  | 254,786 |
Investments [Member] |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Beginning Balance, December 31, 2020 |  |  | 305,250 |
OCI before reclassifications |  |  | (54,582) |
Amounts reclassified from AOCI |  |  | 2,672 |
Other comprehensive income (loss) |  |  | (51,910) |
Ending Balance, June 30, 2021 | 253,340 |  | 253,340 |
Accumulated Other-than-Temporary Impairment [Member] |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Beginning Balance, December 31, 2020 |  |  | (2,546) |
OCI before reclassifications |  |  | (1,055) |
Amounts reclassified from AOCI, Credit loss related |  |  | 2,153 |
Other comprehensive income (loss) |  |  | 1,098 |
Ending Balance, June 30, 2021 | (1,448) |  | (1,448) |
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Held-to-maturity Securities [Member] |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Beginning Balance, December 31, 2020 |  |  | 6 |
OCI before reclassifications |  |  | 0 |
Amounts reclassified from AOCI, HTM related |  |  | (4) |
Other comprehensive income (loss) |  |  | (4) |
Ending Balance, June 30, 2021 | 2 |  | 2 |
Accumulated Defined Benefit Plans Adjustment [Member] |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Beginning Balance, December 31, 2020 |  |  | (85,064) |
OCI before reclassifications, Defined Benefit Pension and Post Retirement Plans |  |  | 0 |
Amount reclassified into net income: Net actuarial loss |  |  | 1,095 |
Ending Balance, June 30, 2021 | (83,969) |  | (83,969) |
Accumulated other comprehensive income (loss) [Member] |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Beginning Balance, December 31, 2020 |  |  | 220,186 |
OCI before reclassifications |  |  | (54,582) |
Amounts reclassified from AOCI |  |  | 3,767 |
Other comprehensive income (loss) | 34,771 | $ 174,083 | (50,815) | $ 70,216
Ending Balance, June 30, 2021 | $ 169,371 |  | $ 169,371 |

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