Consolidated Statement of Cash Flows (Statement) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Net Income (Loss) Attributable to Parent	$ 126,734,000	$ 148,351,000	$ 153,945,000
Provision for (recovery of) credit losses	2,904,000	4,557,000	(11,916,000)
Amortization of Deferred Loan Origination Fees, Net	(8,759,000)	(12,085,000)	(25,185,000)
Goodwill, Purchase Accounting Adjustments	664,000	(334,000)	(1,519,000)
Depreciation	14,015,000	13,819,000	13,267,000
Accretion (Amortization) of Discounts and Premiums, Investments	3,794,000	3,666,000	2,174,000
Deferred Income Tax Expense (Benefit)	(703,000)	611,000	(3,131,000)
Gain (Loss) on Sale of Investments	(7,875,000)	0	0
Gain on equity securities, net	971,000	2,955,000	5,011,000
Share-based Payment Arrangement, Noncash Expense	8,010,000	7,199,000	8,021,000
Payments for Loan Originations, Loans to be Sold in Secondary Market	65,211,000	173,880,000	569,080,000
Proceeds From Loan Sales	65,338,000	185,361,000	609,377,000
Gain (Loss) on Sale of Loans and Leases		495,000
Gains (Losses) on Sales of Other Real Estate	(3,000)	5,611,000	(4,000)
Real Estate Owned, Valuation Allowance, Valuation Increase	(60,000)	(12,039,000)	(64,000)
Gain (Loss) on Sale of Other Loans and Leases	0	(495,000)	0
Bank Owned Life Insurance Income	5,338,000	6,100,000	4,897,000
Amortization Method Qualified Affordable Housing Project Investments, Amortization	8,265,000	7,743,000	7,313,000
Increase (Decrease) in Other Operating Assets and Liabilities, Net [Abstract]
Increase (Decrease) in Other Operating Assets	(2,182,000)	4,467,000	(12,406,000)
Increase (Decrease) in Other Operating Liabilities	(6,982,000)	(4,814,000)	(7,939,000)
Net cash provided by operating activities	150,504,000	134,862,000	157,332,000
Net Cash Provided by (Used in) Investing Activities [Abstract]
Proceeds from Sale of Federal Home Loan Bank Stock	11,672,000	2,216,000	8,677,000
Proceeds from Sale of Debt Securities	284,454,000	0	934,000
Proceeds from Sale, Maturity and Collection of Investments [Abstract]
Proceeds from Sale and Maturity of Debt Securities, Available-for-sale	145,310,000	186,123,000	232,197,000
Payments to Acquire Investments [Abstract]
Payments to Acquire Debt Securities, Available-for-sale	3,981,000	317,278,000	953,900,000
Payments to Acquire Available-for-sale Securities, Equity	2,195,000	9,165,000	0
Payments to Acquire Federal Home Loan Bank Stock	(18,228,000)	0	0
Payments for (Proceeds from) Investments	1,886,000	331,000	2,597,000
Payments for (Proceeds from) Loans and Leases	329,810,000	271,753,000	(312,187,000)
Proceeds from Sale of Other Loans Held-for-sale	0	4,345,000	3,718,000
Proceeds from Sale of Other Real Estate	965,000	17,684,000	758,000
Proceeds from Life Insurance Policy	1,816,000	9,587,000	5,598,000
Payment to Acquire Life Insurance Policy, Investing Activities	(10,779,000)	(7,500,000)	0
Payments for Affordable Housing Programs	9,364,000	10,352,000	10,814,000
Payments to Acquire Property, Plant, and Equipment	7,589,000	7,937,000	14,093,000
Net cash used in investing activities	64,157,000	(403,699,000)	(412,141,000)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Increase (Decrease) in Deposits	(386,901,000)	(456,922,000)	605,168,000
(Increase) decrease in one way sell deposits	194,752,000	787,116,000	(272,952,000)
Proceeds from (Repayments of) Short-term Debt	100,840,000	(11,444,000)	(103,444,000)
Repayments of Long-term Debt	0	0	32,500,000
Payments Related to Tax Withholding for Share-based Compensation	2,844,000	2,761,000	2,403,000
Payments for Repurchase of Common Stock	23,017,000	0	16,048,000
Payments of Ordinary Dividends	68,951,000	76,604,000	74,306,000
Net cash (used in) provided by financing activities	(186,121,000)	239,385,000	103,515,000
Cash and Cash Equivalents, Period Increase (Decrease), Total	28,540,000	(29,452,000)	(151,294,000)
Cash and Cash Equivalents, at Carrying Value, Beginning Balance	189,728,000	219,180,000	370,474,000
Cash and Cash Equivalents, at Carrying Value, Ending Balance	218,268,000	189,728,000	219,180,000
Supplemental Cash Flow Information [Abstract]
Interest Paid, Excluding Capitalized Interest, Operating Activities	95,183,000	30,818,000	16,704,000
Income Taxes Paid	17,200,000	24,670,000	25,505,000
Noncash Investing and Financing Items [Abstract]
Real Estate Owned, Transfer to Real Estate Owned	1,097,000	13,418,000	150,000
Transfer of Portfolio Loans and Leases to Held-for-sale	0	3,890,000	3,718,000
Other Significant Noncash Transaction, Value of Consideration Received	545,000	7,867,000	1,190,000
Affordable Housing Program Obligation, Period Increase (Decrease)	10,000,000	10,000,000	10,000,000
Transfer to Investments	2,745,000	16,250,000	3,000,000
Mortgages [Member]
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Gain (Loss) on Sale of Loans and Leases	1,213,000	4,243,000	18,018,000
Consumer Portfolio Segment [Member]
Increase (Decrease) in Other Operating Assets and Liabilities, Net [Abstract]
Increase (Decrease) in Prepaid Expense	$ (43,000)	$ (9,422,000)	$ (2,415,000)