Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Before Tax Amount
Income (loss) before tax amount		$ 21,269	$ 25,986	$ 68,286	$ 67,578
Net unrealized gains (losses) on available-for-sale investment securities, before tax amount
Net unrealized holding losses arising during the period		(12,622)	(18,093)	(10,411)	(53,798)
Reversal of provision for credit losses		0	(393)	397	370
Less: reclassification adjustment for net gains on sales realized in net income				0	(30)
Other comprehensive income (loss), securities, available-for-sale, adjustment, before tax		(12,622)	(18,486)	(10,014)	(53,458)
Net unrealized gains (losses) on interest rate swaps used in cash flow hedges, before tax amount
Net unrealized holding losses arising during the period		(2,541)	(9,418)	(6,716)	(7,716)
Less: reclassification adjustment for net losses (gains) realized in net income (1)	[1]	1,558	(422)	3,989	(1,040)
Total net unrealized losses on interest rate swaps used in cash flow hedges		(983)	(9,840)	(2,727)	(8,756)
Defined benefit pension plans, Before Tax Amount
Amortization of net actuarial loss included in net periodic pension costs	[2]	247	219	739	655
Total defined benefit pension plans		247	219	739	655
Other comprehensive income (loss), before tax amount		(13,358)	(28,107)	(12,002)	(61,559)
Total comprehensive income (loss), before tax amount		7,911	(2,121)	56,284	6,019
Tax Expense (Benefit)
Income tax expense		4,253	5,185	13,436	13,294
Net unrealized gains (losses) on available-for-sale investment securities, tax expense (benefit)
Other comprehensive income (loss), securities, available-for-sale, unrealized holding gain (loss) arising during period, tax		(2,651)	(3,800)	(2,186)	(11,298)
(Reversal of provision) provision for credit losses, tax		0	(82)	83	78
Less: reclassification adjustment for net gains on sales realized in net income				0	(6)
Total net unrealized losses on available-for-sale investment securities		(2,651)	(3,882)	(2,103)	(11,226)
Net unrealized gains (losses) on interest rate swaps used in cash flow hedges, tax expense (benefit)
Net unrealized holding losses arising during the period		(534)	(1,978)	(1,411)	(1,621)
Less: reclassification adjustment for net losses (gains) realized in net income (1)	[1]	327	(89)	838	(218)
Total net unrealized losses on interest rate swaps used in cash flow hedges		(207)	(2,067)	(573)	(1,839)
Defined benefit pension plans, tax expense (benefit)
Amortization of net actuarial loss included in net periodic pension costs	[2]	52	46	156	138
Other comprehensive (income) loss, defined benefit plan, after reclassification adjustment, tax		52	46	156	138
Other comprehensive income (loss), tax expense (benefit)		(2,806)	(5,903)	(2,520)	(12,927)
Total comprehensive income (loss), tax expense (benefit)		1,447	(718)	10,916	367
Net of Tax Amount
Net income		17,016	20,801	54,850	54,284
Net unrealized gains (losses) on available-for-sale investment securities, net of tax amount
Net unrealized holding losses arising during the period		(9,971)	(14,293)	(8,225)	(42,500)
Reversal of provision for credit losses		0	311	(314)	(292)
Less: reclassification adjustment for net gains on sales realized in net income				0	(24)
Other comprehensive income (loss), securities, available-for-sale, adjustment, after tax		(9,971)	(14,604)	(7,911)	(42,232)
Net unrealized gains (losses) on interest rate swaps used in cash flow hedges, net of tax amount
Net unrealized holding losses arising during the period		(2,007)	(7,440)	(5,305)	(6,095)
Less: reclassification adjustment for net losses (gains) realized in net income (1)	[1]	1,231	(333)	3,151	(822)
Total net unrealized losses on interest rate swaps used in cash flow hedges		(776)	(7,773)	(2,154)	(6,917)
Defined benefit pension plans, net of tax amount
Amortization of net actuarial loss included in net periodic pension costs	[2]	195	173	583	517
Other comprehensive (income) loss, defined benefit plan, after reclassification adjustment, after tax		195	173	583	517
Other comprehensive income (loss), net of tax amount		(10,552)	(22,204)	(9,482)	(48,632)
Total comprehensive income (loss), net of tax amount		$ 6,464	$ (1,403)	$ 45,368	$ 5,652

[1] (1) Included in interest expense on demand deposits on the condensed consolidated statements of income (before tax amount).

[2] (2) These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (before tax amount). See Note 8, "Retirement Plans and Other Postretirement Benefits" for additional details. Note: See accompanying notes to the unaudited condensed consolidated financial statements.