Note 13 - Condensed Financial Statements of Parent Company (Details) - Condensed Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash Flows from Operating Expenses
Net income	$ 17,790	$ 17,747	$ 17,638
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of premiums and accretion of discounts, net	171	224	217
Depreciation expense	726	764	799
Net change in other assets	1,865	35	580
Net change in other liabilities	83	(175)	(4,135)
Losses on securities	(59)	(104)	(90)
Cash Flows from Investing Activities
Purchases of securities available for sale	(83,996)	(171,577)	(64,567)
Maturities and calls of securities available for sale	63,884	151,051	74,934
Cash Flows from Financing Activities
Cash dividends paid	(7,781)	(7,639)	(6,938)
Exercise of stock options		119	92
Net change in cash	(1,500)	2,886	2,039
NBI [Member]
Cash Flows from Operating Expenses
Net income	17,790	17,747	17,638
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed net income of subsidiaries	(10,545)	(10,512)	(10,757)
Amortization of premiums and accretion of discounts, net		1	1
Depreciation expense	17	12	9
Net change in refundable income taxes due from subsidiaries	77	77
Net change in other assets	3	(199)	147
Net change in other liabilities	20	(124)	(364)
Losses on securities	94
Net cash provided by operating activities	7,456	7,002	6,674
Cash Flows from Investing Activities
Purchases of securities available for sale	(614)	(815)	(1,973)
Maturities and calls of securities available for sale	945	1,352	2,250
Net cash provided by investing activities	331	537	277
Cash Flows from Financing Activities
Cash dividends paid	(7,781)	(7,639)	(6,938)
Exercise of stock options		119	92
Capital distribution to subsidiary			(105)
Net cash used in financing activities	(7,781)	(7,520)	(6,951)
Net change in cash	6	19
Cash due from subsidiaries at beginning of year	21	2	2
Cash due from subsidiaries at end of year	$ 27	$ 21	$ 2