Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities
Net income	$ 31,274,000	$ 31,913,000	$ 27,020,000
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	10,358,000	9,576,000	11,654,000
Accretion of acquired loans	(2,338,000)	(4,925,000)	(5,338,000)
Provision for loan losses	2,950,000	2,900,000	(1,000,000)
Deferred income tax expense (benefit)	831,000	(812,000)	4,412,000
Stock-based compensation expense	1,981,000	1,459,000	684,000
Stock grants to directors for retainer fee	363,000	327,000	403,000
Proceeds from sales of mortgage loans held for sale	111,311,000	114,757,000	120,880,000
Origination of mortgage loans held for sale	(108,857,000)	(110,778,000)	(116,997,000)
Net gain on sales of mortgage loans held for sale	(3,972,000)	(3,699,000)	(3,626,000)
Gain on trust preferred securities repurchase	0	(2,970,000)	0
Net gain from sales and valuation write-downs of foreclosed assets	(319,000)	(520,000)	(62,000)
Net loss from sales and valuation write-downs of former bank premises	133,000	35,000	0
Net loss from sales and disposals of premises and equipment	71,000	174,000	55,000
Net (gain) loss from sales of available for sale securities	(37,000)	1,000	(17,000)
Earnings on bank owned life insurance	(2,731,000)	(1,264,000)	(1,113,000)
Net change in:
Accrued interest receivable	(1,056,000)	122,000	(321,000)
Other assets	(354,000)	(648,000)	(4,815,000)
Accrued interest and other liabilities	(943,000)	(1,046,000)	4,185,000
Net cash from operating activities	38,665,000	34,602,000	36,004,000
Cash flows from investing activities
Purchases of securities available for sale	(67,027,000)	(164,336,000)	(10,645,000)
Proceeds from maturities, calls and repayments of securities available for sale	52,504,000	172,173,000	93,873,000
Proceeds from sales of securities available for sale	7,619,000	264,000	1,483,000
Purchases of Federal Home Loan Bank stock	(3,010,000)	(459,000)	0
Proceeds from Federal Home Loan Bank stock redemption	0	0	6,132,000
Loan originations and payments, net	(178,373,000)	(97,282,000)	(188,932,000)
Purchases of bank owned life insurance	(1,500,000)	(7,000,000)	0
Proceeds from bank owned life insurance cash value release and death benefits	2,720,000	0	0
Purchases of premises and equipment, net	(5,423,000)	(2,025,000)	(1,081,000)
Proceeds from sales of former bank premises	25,000	45,000	0
Proceeds from sales of foreclosed assets	993,000	2,059,000	2,967,000
Net cash for investing activities	(191,472,000)	(96,561,000)	(96,203,000)
Cash flows from financing activities
Net decrease in time deposits	(55,839,000)	(20,854,000)	(147,106,000)
Net increase in all other deposits	203,219,000	120,457,000	146,944,000
Net decrease in securities sold under agreements to repurchase	(12,962,000)	(23,061,000)	(12,798,000)
Proceeds from Federal Home Loan Bank advances	90,000,000	110,000,000	20,000,000
Maturities of Federal Home Loan Bank advances	(45,000,000)	(3,000,000)	(6,000,000)
Proceeds from stock option exercises, net of cashless exercises	318,000	978,000	891,000
Employee stock purchase plan	46,000	36,000	44,000
Dividend reinvestment plan	1,576,000	1,601,000	655,000
Repurchase of common stock	0	(3,732,000)	(15,762,000)
Repurchase of trust preferred securities	0	(8,030,000)	0
Payment of cash dividends to common shareholders	(12,046,000)	(18,731,000)	(9,516,000)
Net cash from (for) financing activities	169,312,000	155,664,000	(22,648,000)
Net change in cash and cash equivalents	16,505,000	93,705,000	(82,847,000)
Cash and cash equivalents at beginning of period	183,596,000	89,891,000	172,738,000
Cash and cash equivalents at end of period	200,101,000	183,596,000	89,891,000
Supplemental disclosures of cash flows information
Interest	15,468,000	12,477,000	11,618,000
Federal income taxes	14,225,000	15,125,000	8,000,000
Noncash financing and investing activities:
Transfers from loans to foreclosed assets	887,000	414,000	2,203,000
Transfers from bank premises to other real estate owned	$ 1,736,000	$ 381,000	$ 0