Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Before Tax Amount
Income (loss) before tax amount		$ 26,173	$ 23,197	$ 92,340	$ 25,250
Net unrealized gains (losses) on available-for-sale investment securities, before tax amount
Net unrealized holding (losses) gains arising during the period		(1,378)	726	1,604	2,930
Provision (reversal of provision) for credit losses		(330)	163	54	(392)
Less: reclassification adjustment for net gains on sales realized in net income	[1]	(21)	(57)	(140)	(817)
Other comprehensive income (loss), securities, available-for-sale, adjustment, before tax		(1,069)	506	1,410	2,505
Net unrealized gains (losses) on interest rate swaps used in cash flow hedges, before tax amount
Net unrealized holding (losses) gains arising during the period		(7)	5	(5)	(554)
Less: reclassification adjustment for net losses realized in net income (2)	[2]	77	78	229	176
Total net unrealized gains on interest rate swaps used in cash flow hedges		70	83	224	(378)
Defined benefit pension plans, Before Tax Amount
Amortization of net actuarial loss included in net periodic pension costs	[3]	329	307	987	901
Total defined benefit pension plans		329	307	987	901
Other comprehensive income (loss), before tax amount		(670)	896	2,621	3,028
Total comprehensive income (loss), before tax amount		25,503	24,093	94,961	28,278
Tax Expense (Benefit)
Income tax expense		5,262	5,078	17,951	4,208
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		(292)	153	336	615
Provision (reversal of provision) for credit losses		(70)	35	11	(82)
Less: reclassification adjustment for net gains on sales realized in net income	[1]	(4)	(12)	(29)	(172)
Total net unrealized (losses) gains on available-for-sale investment securities		(226)	106	296	525
Net unrealized gains (losses) on interest rate swaps used in cash flow hedges, tax expense (benefit)
Net unrealized holding (losses) gains arising during the period		(1)	2	(1)	(116)
Less: reclassification adjustment for net losses realized in net income (2)	[2]	16	16	48	37
Total net unrealized gains on interest rate swaps used in cash flow hedges		15	18	47	(79)
Defined benefit pension plans, tax expense (benefit)
Amortization of net actuarial loss included in net periodic pension costs	[3]	69	65	207	189
Other comprehensive (income) loss, defined benefit plan, after reclassification adjustment, tax		69	65	207	189
Other comprehensive income (loss), tax expense (benefit)		(142)	189	550	635
Total comprehensive income (loss), tax expense (benefit)		5,120	5,267	18,501	4,843
Net of Tax Amount
Net income		20,911	18,119	74,389	21,042
Net unrealized gains (losses) on available-for-sale investment securities, net of tax amount
Net unrealized holding (losses) gains arising during the period		(1,086)	573	1,268	2,315
Provision (reversal of provision) for credit losses		(260)	128	43	(310)
Less: reclassification adjustment for net gains on sales realized in net income	[1]	(17)	(45)	(111)	(645)
Other comprehensive income (loss), securities, available-for-sale, adjustment, after tax		(843)	400	1,114	1,980
Net unrealized gains (losses) on interest rate swaps used in cash flow hedges, net of tax amount
Net unrealized holding (losses) gains arising during the period		(6)	3	(4)	(438)
Less: reclassification adjustment for net losses realized in net income (2)	[2]	61	62	181	139
Total net unrealized gains on interest rate swaps used in cash flow hedges		55	65	177	(299)
Defined benefit pension plans, net of tax amount
Amortization of net actuarial loss included in net periodic pension costs	[3]	260	242	780	712
Other comprehensive (income) loss, defined benefit plan, after reclassification adjustment, after tax		260	242	780	712
Other comprehensive income (loss), net of tax amount		(528)	707	2,071	2,393
Total comprehensive income (loss), net of tax amount		$ 20,383	$ 18,826	$ 76,460	$ 23,435

[1] (1) Included in net gain on sales of investment securities on the consolidated statements of income (before tax amount).

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

[3] (3) 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.