Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities
Net income	$ 10,881,000	$ 7,615,000
Adjustments to reconcile net income to net cash from operating activities
Depreciation and amortization	2,483,000	2,548,000
Accretion of acquired loans	(357,000)	(483,000)
Provision for loan losses	0	600,000
Stock-based compensation expense	597,000	476,000
Stock grants to directors for retainer fees	0	2,000
Proceeds from sales of mortgage loans held for sale	21,010,000	19,317,000
Origination of mortgage loans held for sale	(19,585,000)	(19,342,000)
Net gain from sales of mortgage loans held for sale	(736,000)	(867,000)
Net gain from sales and valuation write-downs of foreclosed assets	(105,000)	(43,000)
Net loss from sales and valuation write-downs of former bank premises	99,000	15,000
Net loss from sales and write-downs of fixed assets	53,000	40,000
Earnings on bank owned life insurance	(331,000)	(1,738,000)
Net change in:
Accrued interest receivable	(820,000)	(828,000)
Other assets	(866,000)	(321,000)
Accrued interest and other liabilities	722,000	980,000
Net cash from operating activities	13,045,000	7,971,000
Cash flows from investing activities
Loan originations and payments, net	7,257,000	(61,701,000)
Purchases of securities available for sale	(13,303,000)	(14,701,000)
Proceeds from maturities, calls and repayments of securities available for sale	4,609,000	10,858,000
Purchases of Federal Home Loan Bank stock	0	(1,210,000)
Proceeds from sales of foreclosed assets	410,000	99,000
Proceeds from bank owned life insurance cash value release and death benefits	0	2,720,000
Net purchases of premises and equipment	(1,429,000)	(1,138,000)
Net cash for investing activities	(2,456,000)	(65,073,000)
Cash flows from financing activities
Net decrease in time deposits	(8,412,000)	(55,203,000)
Net increase (decrease) in all other deposits	26,100,000	(41,766,000)
Net decrease in securities sold under agreements to repurchase	(13,854,000)	(5,031,000)
Maturities of Federal Home Loan Bank advances	0	(10,000,000)
Proceeds from Federal Home Loan Bank advances	0	40,000,000
Proceeds from stock option exercises	54,000	248,000
Employee stock purchase plan	14,000	12,000
Dividend reinvestment plan	164,000	1,145,000
Payment of cash dividends to common shareholders	(3,599,000)	(2,923,000)
Net cash from (for) financing activities	467,000	(73,518,000)
Net change in cash and cash equivalents	11,056,000	(130,620,000)
Cash and cash equivalents at beginning of period	200,101,000	183,596,000
Cash and cash equivalents at end of period	211,157,000	52,976,000
Supplemental disclosures of cash flows information
Interest	4,529,000	3,322,000
Federal income tax	0	0
Noncash financing and investing activities:
Transfers from loans to foreclosed assets	232,000	97,000
Transfers from bank premises to other real estate owned	$ 296,000	$ 0