CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 84,337,000	$ 87,047,000	$ 80,411,000
Adjustments to reconcile net income to net cash from operating activities:
Depreciation	6,042,000	5,930,000	5,654,000
Provision for loan losses	14,770,000	3,235,000	6,400,000
Net loss on sale and write down of other real estate owned	0	0	16,000
Amortization of loan servicing rights	772,000	528,000	503,000
Net change in loan servicing rights valuation allowance	715,000	0	0
Loans originated for sale	(117,600,000)	(66,008,000)	(49,816,000)
Net gain on sales of loans	(4,510,000)	(2,043,000)	(1,713,000)
Proceeds from sale of loans	114,244,000	64,820,000	51,715,000
Net (gain) loss on sale of premises and equipment	86,000	(3,000)	1,000
Net (gain) loss on sales and calls of securities available-for-sale	(433,000)	(142,000)	50,000
Net amortization of available -for-sale securities	3,998,000	3,947,000	3,177,000
Stock based compensation expense	1,790,000	4,187,000	5,608,000
Earnings on life insurance	(2,105,000)	(1,890,000)	(1,244,000)
Gain on life insurance	(730,000)	(841,000)	(206,000)
Tax benefit of stock award issuances	(71,000)	(529,000)	(761,000)
Net change:
Interest receivable and other assets	(6,315,000)	(4,733,000)	(3,301,000)
Interest payable and other liabilities	(7,762,000)	6,534,000	8,481,000
Total adjustments	2,891,000	12,992,000	24,564,000
Net cash from operating activities	87,228,000	100,039,000	104,975,000
Cash flows from investing activities:
Proceeds from sale of securities available-for-sale	8,018,000	57,114,000	15,302,000
Proceeds from maturities, calls and principal paydowns of securities available-for-sale	97,998,000	67,818,000	53,817,000
Purchases of securities available-for-sale	(216,478,000)	(129,453,000)	(126,551,000)
Purchase of life insurance	(10,409,000)	(5,552,000)	(423,000)
Net increase in total loans	(587,377,000)	(152,119,000)	(101,670,000)
Proceeds from sales of land, premises and equipment	658,000	14,000	461,000
Purchases of land, premises and equipment	(5,719,000)	(7,998,000)	(7,968,000)
Proceeds from sales of other real estate owned	0	0	21,000
Proceeds from life insurance	1,285,000	1,483,000	569,000
Net cash from investing activities	(712,024,000)	(168,693,000)	(166,442,000)
Cash flows from financing activities:
Net increase in total deposits	902,986,000	89,754,000	35,410,000
Net increase (decrease) in short-term borrowings	10,500,000	(75,555,000)	174,903,000
Payments on short-term FHLB borrowings	(170,000,000)	0	(80,000,000)
Payments on long-term FHLB borrowings	0	0	(30,000)
Proceeds from long-term FHLB borrowings	75,000,000	0	0
Payments on subordinated debentures	0	(30,928,000)	0
Common dividends paid	(30,566,000)	(29,639,000)	(25,278,000)
Preferred dividends paid	(13,000)	(13,000)	(13,000)
Payments related to equity incentive plan	(2,137,000)	(2,109,000)	(2,435,000)
Purchase of treasury stock	(10,547,000)	(515,000)	(463,000)
Sales of treasury stock	119,000	118,000	115,000
Net cash from financing activities	775,342,000	(48,887,000)	102,209,000
Net change in cash and cash equivalents	150,546,000	(117,541,000)	40,742,000
Cash and cash equivalents at beginning of the year	99,381,000	216,922,000	176,180,000
Cash and cash equivalents at end of the year	249,927,000	99,381,000	216,922,000
Cash paid during the period for:
Interest	35,740,000	58,964,000	43,606,000
Income taxes	19,335,000	21,035,000	19,033,000
Supplemental non-cash disclosures:
Loans transferred to other real estate owned	35,000	0	316,000
Property transferred to held for sale	0	0	221,000
Right-of-use assets obtained in exchange for lease liabilities	$ 0	$ 5,483,000	$ 0