Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Changes in accumulated other comprehensive income by component
Beginning balance	$ 1,552,449	$ 1,513,275	$ 1,551,317	$ 1,491,486
Other comprehensive (loss)/income before reclassification adjustments	(3,061)	(15,982)	(6,605)	(2,965)
Amounts reclassified from accumulated other comprehensive income	26,401	5,254	26,013	4,872
Other comprehensive income/(loss)	23,340	(10,728)	19,408	1,907
Ending balance	1,556,598	1,511,501	1,556,598	1,511,501
Unrealized holding losses, tax	168	3,771	1,926	463
Reclassification adjustment for gains or losses on securities available-for-sale, tax	(7,706)	(1,731)	(7,706)	(1,731)
Unrealized holding losses on interest rate swaps, tax	(96)	(508)	(726)	(508)
Reclassification adjustment for gains or losses on defined benefit pension plan, tax	147	152	294	304
Total
Changes in accumulated other comprehensive income by component
Beginning balance	(153,424)	(158,523)	(149,492)	(171,158)
Other comprehensive income/(loss)	23,340	(10,728)	19,408	1,907
Ending balance	(130,084)	(169,251)	(130,084)	(169,251)
Unrealized losses on securities available-for-sale
Changes in accumulated other comprehensive income by component
Beginning balance	(156,357)	(151,189)	(150,659)	(164,206)
Other comprehensive (loss)/income before reclassification adjustments	(3,391)	(17,719)	(9,089)	(4,702)
Amounts reclassified from accumulated other comprehensive income	26,789	5,636	26,789	5,636
Other comprehensive income/(loss)	23,398	(12,083)	17,700	934
Ending balance	(132,959)	(163,272)	(132,959)	(163,272)
Change in fair value of interest rate swaps
Changes in accumulated other comprehensive income by component
Beginning balance	1,780	0	(374)	0
Other comprehensive (loss)/income before reclassification adjustments	330	1,737	2,484	1,737
Amounts reclassified from accumulated other comprehensive income	0	0	0	0
Other comprehensive income/(loss)	330	1,737	2,484	1,737
Ending balance	2,110	1,737	2,110	1,737
Change in defined benefit pension plans
Changes in accumulated other comprehensive income by component
Beginning balance	1,153	(7,334)	1,541	(6,952)
Other comprehensive (loss)/income before reclassification adjustments	0	0	0	0
Amounts reclassified from accumulated other comprehensive income	(388)	(382)	(776)	(764)
Other comprehensive income/(loss)	(388)	(382)	(776)	(764)
Ending balance	$ 765	$ (7,716)	$ 765	$ (7,716)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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