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Accumulated Other Comprehensive Income - Unrealized gains (losses) (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2024 | Jun. 30, 2023 | Jun. 30, 2024 | Jun. 30, 2023
Accumulated Other Comprehensive Income (Loss) |  |  |  |
Beginning balance | $ (138,110) | $ (125,589) | $ (127,087) | $ (139,974)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent | 3,609 | (15,661) | (7,414) | (1,276)
Ending balance | (134,501) | (141,250) | (134,501) | (141,250)
Unrealized gains and (Losses) on available- for-sale Securities |  |  |  |
Accumulated Other Comprehensive Income (Loss) |  |  |  |
Beginning balance | (129,096) | (114,658) | (118,000) | (128,896)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent | 3,535 | (15,808) | (7,561) | (1,570)
Ending balance | (125,561) | (130,466) | (125,561) | (130,466)
Unrealized gains (losses) on securities available-for-sale without other than temporary impairment |  |  |  |
Accumulated Other Comprehensive Income (Loss) |  |  |  |
Beginning balance | (131,262) | (116,844) | (120,252) | (131,135)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent | 3,532 | (15,827) | (7,478) | (1,536)
Ending balance | (127,730) | (132,671) | (127,730) | (132,671)
Unrealized gains (losses) on securities available-for-sale with other than temporary impairment |  |  |  |
Accumulated Other Comprehensive Income (Loss) |  |  |  |
Beginning balance | 2,166 | 2,186 | 2,252 | 2,239
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent | 3 | 19 | (83) | (34)
Ending balance | 2,169 | 2,205 | 2,169 | 2,205
Retirement plans |  |  |  |
Accumulated Other Comprehensive Income (Loss) |  |  |  |
Beginning balance | (9,014) | (10,931) | (9,087) | (11,078)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent | 74 | 147 | 147 | 294
Ending balance | $ (8,940) | $ (10,784) | $ (8,940) | $ (10,784)

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- Definition Amount, after tax, of accumulated increase (decrease) in equity from transaction and other event and circumstance from nonowner source. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -Publisher FASB -URI https://asc.fasb.org/1943274/2147482790/220-10-45-14A Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 11 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482790/220-10-45-11 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (g)(2)(ii) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480016/944-40-65-2 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (h)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480016/944-40-65-2 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(30)(a)(4)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(23)(a)(3)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1 Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482790/220-10-45-14 + Details
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