CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash Flows From Operating Activities:
Net income	$ 30,059,000	$ 34,904,000	$ 28,604,000
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of intangible assets	780,000	680,000	859,000
Net amortization of premium/discount on investment securities	4,473,000	6,275,000	7,328,000
Depreciation	4,189,000	4,021,000	4,313,000
Losses (gains) on sales of securities	173,000	(15,000)	(51,000)
Stock-based compensation expense	4,139,000	6,732,000	2,859,000
(Release of) provision for credit losses	(550,000)	1,350,000	(130,000)
Deferred income tax benefit	(284,000)	(1,163,000)	(698,000)
(Decrease) increase in current income tax liability	(1,481,000)	724,000	206,000
Increase (decrease) in pension liability	806,000	(2,484,000)	(1,811,000)
Increase in accounts receivable	(3,841,000)	(2,520,000)	(602,000)
Other operating activities, net	(1,527,000)	3,104,000	(6,330,000)
Net cash provided by operating activities	36,936,000	51,608,000	34,547,000
Cash Flows From Investing Activities:
Proceeds from sales of securities available-for-sale	111,583,000	3,838,000	63,774,000
Proceeds from maturities of securities available-for-sale	39,233,000	61,209,000	96,951,000
Purchases of securities available-for-sale	(15,332,000)	(232,083,000)	(494,226,000)
Net decrease (increase) in loans	68,588,000	(122,326,000)	(68,664,000)
Purchase of bank-owned life insurance	0	(4,000,000)	(25,119,000)
Decrease (increase) in payments in advance of funding	94,914,000	(2,348,000)	(96,864,000)
Purchases of premises and equipment, net	(14,324,000)	(5,866,000)	(4,369,000)
Asset acquisition of TouchPoint	0	(4,814,000)	0
Net cash provided by (used in) investing activities	284,662,000	(306,390,000)	(528,517,000)
Cash Flows From Financing Activities:
Net (decrease) increase in noninterest-bearing demand deposits	(118,398,000)	60,115,000	89,138,000
Net (decrease) increase in interest-bearing demand and savings deposits	(34,106,000)	(17,838,000)	90,310,000
Net increase (decrease) in time deposits	36,101,000	(6,563,000)	(8,801,000)
Net (increase) decrease in accounts and drafts receivable from customers	(14,872,000)	(90,787,000)	6,000
Net increase in accounts and drafts payable	3,769,000	17,204,000	215,010,000
Cash dividends paid	(15,959,000)	(15,442,000)	(15,446,000)
Purchase of common shares for treasury	(5,773,000)	(5,299,000)	(30,997,000)
Other financing activities, net	(834,000)	(594,000)	(850,000)
Net cash (used in) provided by financing activities	(150,072,000)	(59,204,000)	338,370,000
Net increase (decrease) in cash and cash equivalents	171,526,000	(313,986,000)	(155,600,000)
Cash and cash equivalents at beginning of year	200,942,000	514,928,000	670,528,000
Cash and cash equivalents at end of year	372,468,000	200,942,000	514,928,000
Supplemental information:
Cash paid for interest	15,697,000	3,431,000	1,194,000
Cash paid for income taxes	$ 9,300,000	$ 8,396,000	$ 5,637,000