Note 12 - Condensed Financial Statements of Parent Company - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flows from Operating Activities
Net income	$ 16,151	$ 14,092	$ 14,942
Adjustment to reconcile net income to net cash provided by operating activities:
Amortization of premiums and accretion of discounts, net	58	58	89
Gain on sale of securities	(17)	(14)	(232)
Other assets	2,886	(2,537)	438
Net change in other liabilities	404	101	(41)
Net cash provided by operating activities	19,775	10,994	17,533
Cash Flows from Investing Activities
Net change in interest-bearing deposits	7,742	29,035	50,543
Maturities, sales and calls of securities available for sale	50,438	13,812	220,581
Maturities and calls of securities held to maturity	6,430	8,975	16,945
Net cash used in investing activities	(3,608)	(20,193)	(32,223)
Cash Flows from Financing Activities
Cash dividends paid	(8,419)	(8,141)	(8,071)
Net cash provided by (used in) financing activities	(16,211)	8,151	16,512
Net change in cash	(44)	(1,048)	1,822
Parent Company [Member]
Cash Flows from Operating Activities
Net income	16,151	14,092	14,942
Adjustment to reconcile net income to net cash provided by operating activities:
Equity in undistributed net income of subsidiaries	(7,658)	(6,532)	(5,896)
Amortization of premiums and accretion of discounts, net			1
Gain on sale of securities		(4)
Net change in refundable income taxes due from subsidiaries	(228)	(146)	(223)
Other assets	(109)	(156)	219
Net change in other liabilities	115	(40)	(227)
Net cash provided by operating activities	8,271	7,214	8,816
Cash Flows from Investing Activities
Net change in interest-bearing deposits	146	807	(1,140)
Maturities, sales and calls of securities available for sale		192
Maturities and calls of securities held to maturity			450
Capital distribution to subsidiary		(100)
Net cash used in investing activities	146	899	(690)
Cash Flows from Financing Activities
Cash dividends paid	(8,419)	(8,141)	(8,071)
Net cash provided by (used in) financing activities	(8,419)	(8,141)	(8,071)
Net change in cash	(2)	(28)	55
Cash due from subsidiaries at beginning of year	46	74	19
Cash due from subsidiaries at end of year	$ 44	$ 46	$ 74