Consolidated Statement of Cash Flows (Statement) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash and Cash Equivalents, at Carrying Value, Beginning Balance	$ 167,214	$ 169,112	$ 146,446
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net Income (Loss) Attributable to Parent	102,700	110,387	84,242
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Provision for loan losses	6,171	7,945	8,557
Amortization of Deferred Loan Origination Fees, Net	6,826	6,158	5,758
Goodwill, Purchase Accounting Adjustments	(3,373)	(793)	0
Depreciation	9,119	8,585	8,644
Accretion (Amortization) of Discounts and Premiums, Investments	(1,455)	(1,262)	(1,473)
Long-term Debt, Prepayment Penalty	0	0	5,719
Deferred Income Tax Expense (Benefit)	(844)	538	3,289
Gain (Loss) on Sale of Investments	(421)	(2,271)	1,821
Gain on equity securities, net	5,118	4,616	1,210
Share-based Payment Arrangement, Noncash Expense	6,324	5,063	3,942
Payments for Loan Originations, Loans to be Sold in Secondary Market	338,437	202,827	230,860
Proceeds From Loan Sales	340,637	207,836	242,139
Gain (Loss) on Sales of Loans, Net	0	2,826	0
Other Real Estate Owned Devaluations	225	491	458
Gains (Losses) on Sales of Other Real Estate	(222)	4,235	251
Bank Owned Life Insurance Income	4,557	6,815	4,858
Amortization Method Qualified Affordable Housing Project Investments, Amortization	6,927	7,322	10,278
Increase (Decrease) in Prepaid Expense and Other Assets	0	0	(15,000)
Increase (Decrease) in Other Operating Assets and Liabilities, Net [Abstract]
Increase (Decrease) in Other Operating Assets	(12,305)	(9,413)	1,155
Increase (Decrease) in Other Operating Liabilities	(3,781)	5,131	(11,778)
Net Cash Provided by (Used in) Operating Activities, Total	111,014	131,797	86,686
Net Cash Provided by (Used in) Investing Activities [Abstract]
Payments for (Proceeds from) Federal Home Loan Bank Stock	(14,675)	(7,003)	0
Proceeds from Sale of Debt Securities	91,110	244,399	2,265
Proceeds from Sale, Maturity and Collection of Investments [Abstract]
Proceeds from Sale and Maturity of Held-to-maturity Securities	475	10,547	14,426
Proceeds from Sale and Maturity of Debt Securities, Available-for-sale	195,989	197,826	193,937
Payments to Acquire Investments [Abstract]
Payments to Acquire Held-to-maturity Securities	0	7,133	113,519
Payments to Acquire Debt Securities, Available-for-sale	0	373,372	29,684
Payments to Acquire Available-for-sale Securities, Equity	100	2,590	0
Payments to Acquire Federal Reserve Bank Stock	6,428	0	0
Increase (Decrease) in Equity Securities, FV-NI	(6,429)	(1,153)	(1,305)
Payments for (Proceeds from) Loans and Leases	216,353	57,315	119,336
Proceeds from Sale of Other Loans Held-for-sale	0	3,000	0
Proceeds from Sale of Other Real Estate	1,465	13,094	2,921
Proceeds from Life Insurance Policy	1,571	8,096	1,037
Payment to Acquire Life Insurance Policy, Investing Activities	3,000	0	0
Payments for Affordable Housing Programs	6,038	0	7,000
Payments to Acquire Property, Plant, and Equipment	14,885	11,533	7,018
Payments to Acquire Businesses, Net of Cash Acquired	4,831	(12,270)	0
Net Cash Provided by (Used in) Investing Activities, Total	60,079	45,445	(60,666)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Increase (Decrease) in Deposits	159,696	159,590	295,370
Proceeds from (Repayments of) Short-term Debt	(20,072)	(169,323)	(3,506)
Proceeds from Issuance of Long-term Debt	50,000	50,000	150,000
Repayments of Subordinated Debt	0	0	30,000
Repayments of Long-term Debt	257,500	150,000	350,000
Payments Related to Tax Withholding for Share-based Compensation	827	610	347
Payments for Repurchase of Common Stock	40,535	5,784	7,378
Payments of Ordinary Dividends	69,113	63,013	57,493
Net cash used in financing activities	(178,351)	(179,140)	(3,354)
Increase (decrease) in cash and cash equivalents	(7,258)	(1,898)	22,666
Cash and Cash Equivalents, at Carrying Value, Ending Balance	159,956	167,214	169,112
Supplemental Cash Flow Information [Abstract]
Interest Paid, Excluding Capitalized Interest, Operating Activities	63,038	43,600	42,538
Income Taxes Paid	15,186	7,345	26,190
Noncash Investing and Financing Items [Abstract]
Debt Securities, Held-to-maturity, Transfer, Amount	373,900	0	0
Real Estate Owned, Transfer to Real Estate Owned	1,671	1,204	3,457
Other Significant Noncash Transaction, Value of Consideration Received	11,475	0	0
Other repossessed assets, transfer to repossessed assets	0	11,379	5,553
Affordable Housing Program Obligation, Period Increase (Decrease)	10,000	8,000	7,000
Reported Value Measurement [Member]
Noncash Investing and Financing Items [Abstract]
Debt Securities, Held-to-maturity, Transfer, Amount	349,773
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	7,198	4,879	5,014
Consumer Portfolio Segment [Member]
Increase (Decrease) in Other Operating Assets and Liabilities, Net [Abstract]
Increase (Decrease) in Prepaid Expense	$ (5,358)	$ (1,298)	$ (4,350)