Note 13 - Condensed Financial Statements of Parent Company - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash Flows from Operating Activities
Net income	$ 14,942	$ 15,833	$ 16,914
Adjustment to reconcile net income to net cash provided by operating activities:
Amortization of premiums and accretion of discounts, net	89	117	138
Depreciation of premises and equipment	801	749	732
Loss on disposal of fixed assets		15	94
Other assets	(373)	420	(574)
Net change in other liabilities	(41)	963	(428)
Net cash provided by operating activities	17,533	20,529	20,338
Cash Flows from Investing Activities
Net change in interest-bearing deposits	50,543	(28,263)	(4,482)
Purchases of securities held to maturity			(6,381)
Proceeds from calls and maturities of securities available for sale	220,581	64,556	11,088
Proceeds from calls and maturities of securities held to maturity	16,945	9,205	8,677
Proceeds from sale of premises and equipment			453
Net cash used in investing activities	(32,223)	(49,945)	(35,324)
Cash Flows from Financing Activities
Cash dividends paid	(8,071)	(7,930)	(7,853)
Stock options exercised		173	58
Net cash provided by financing activities	16,512	28,674	14,597
Net change in cash	1,822	(742)	(389)
Parent Company [Member]
Cash Flows from Operating Activities
Net income	14,942	15,833	16,914
Adjustment to reconcile net income to net cash provided by operating activities:
Equity in undistributed net income of subsidiaries	(5,896)	(8,533)	(9,718)
Amortization of premiums and accretion of discounts, net	1	1	1
Depreciation of premises and equipment	0	3	9
Loss on disposal of fixed assets	0	2	94
Net change in refundable income taxes due from subsidiaries	(223)	106	96
Other assets	219	(81)	(63)
Net change in other liabilities	(227)	128	(33)
Net cash provided by operating activities	8,816	7,459	7,300
Cash Flows from Investing Activities
Net change in interest-bearing deposits	(1,140)	307	213
Purchases of securities held to maturity	0	0	(453)
Proceeds from calls and maturities of securities available for sale	0	0	455
Proceeds from calls and maturities of securities held to maturity	450	0	0
Proceeds from sale of premises and equipment	0	0	263
Net cash used in investing activities	(690)	307	478
Cash Flows from Financing Activities
Cash dividends paid	(8,071)	(7,930)	(7,853)
Stock options exercised	0	173	58
Net cash provided by financing activities	(8,071)	(7,757)	(7,795)
Net change in cash	55	9	17
Cash due from subsidiaries at beginning of year	19	10	27
Cash due from subsidiaries at end of year	$ 74	$ 19	$ 10