Note 5 - Fair Value Measurements and Fair Values of Financial Instruments (Details) - Assets Measured at Fair Value - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	$ 497,111	$ 516,807
Nonrecurring fair value measurements
Impaired loans with a valuation allowance	3,880	3,241
Valuation allowance	(600)	(769)
Impaired loans, net	3,880	3,241
US Government Agencies Debt Securities [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	26,871	26,676
Obligations of States and Political Subdivisions, Tax-exempt [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	119,749	124,839
Obligations of States and Political Subdivisions, Taxable [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	35,135	33,878
Collateralized Mortgage Backed Securities [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	76,790	83,903
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	230,794	238,823
Collateralized Debt Obligations [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	34	34
Debt Securities [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	489,373	508,153
Equity Securities [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	7,738	8,654
Estimate of Fair Value Measurement [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	497,111	516,807
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	497,111	516,807
Obligations of states and political subdivisions:
Servicing rights	1,209	1,281
Total recurring fair value measurements	498,320	518,088
Estimate of Fair Value Measurement [Member] | Fair Value, Measurements, Nonrecurring [Member]
Nonrecurring fair value measurements
Impaired loans with a valuation allowance	3,880	3,241
Valuation allowance	(600)	(769)
Impaired loans, net	3,280	2,472
Foreclosed assets held for sale	1,223	1,189
Total nonrecurring fair value measurements	4,503	3,661
Estimate of Fair Value Measurement [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	26,871	26,676
Estimate of Fair Value Measurement [Member] | Obligations of States and Political Subdivisions, Tax-exempt [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	119,749	124,839
Estimate of Fair Value Measurement [Member] | Obligations of States and Political Subdivisions, Taxable [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	35,135	33,878
Estimate of Fair Value Measurement [Member] | Collateralized Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	76,790	83,903
Estimate of Fair Value Measurement [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	230,794	238,823
Estimate of Fair Value Measurement [Member] | Collateralized Debt Obligations [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	34	34
Estimate of Fair Value Measurement [Member] | Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	489,373	508,153
Estimate of Fair Value Measurement [Member] | Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	7,738	8,654
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	7,738	8,654
Obligations of states and political subdivisions:
Servicing rights	0	0
Total recurring fair value measurements	7,738	8,654
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Nonrecurring fair value measurements
Impaired loans with a valuation allowance	0	0
Valuation allowance	0	0
Impaired loans, net	0	0
Foreclosed assets held for sale	0	0
Total nonrecurring fair value measurements	0	0
Fair Value, Inputs, Level 1 [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	0	0
Fair Value, Inputs, Level 1 [Member] | Obligations of States and Political Subdivisions, Tax-exempt [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	0	0
Fair Value, Inputs, Level 1 [Member] | Obligations of States and Political Subdivisions, Taxable [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	0	0
Fair Value, Inputs, Level 1 [Member] | Collateralized Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	0	0
Fair Value, Inputs, Level 1 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	0	0
Fair Value, Inputs, Level 1 [Member] | Collateralized Debt Obligations [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	0	0
Fair Value, Inputs, Level 1 [Member] | Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	0	0
Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	7,738	8,654
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	489,373	508,153
Obligations of states and political subdivisions:
Servicing rights	0	0
Total recurring fair value measurements	489,373	508,153
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Nonrecurring fair value measurements
Impaired loans with a valuation allowance	0	0
Valuation allowance	0	0
Impaired loans, net	0	0
Foreclosed assets held for sale	0	0
Total nonrecurring fair value measurements	0	0
Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	26,871	26,676
Fair Value, Inputs, Level 2 [Member] | Obligations of States and Political Subdivisions, Tax-exempt [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	119,749	124,839
Fair Value, Inputs, Level 2 [Member] | Obligations of States and Political Subdivisions, Taxable [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	35,135	33,878
Fair Value, Inputs, Level 2 [Member] | Collateralized Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	76,790	83,903
Fair Value, Inputs, Level 2 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	230,794	238,823
Fair Value, Inputs, Level 2 [Member] | Collateralized Debt Obligations [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	34	34
Fair Value, Inputs, Level 2 [Member] | Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	489,373	508,153
Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	0	0
Obligations of states and political subdivisions:
Servicing rights	1,209	1,281
Total recurring fair value measurements	1,209	1,281
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Nonrecurring fair value measurements
Impaired loans with a valuation allowance	3,880	3,241
Valuation allowance	(600)	(769)
Impaired loans, net	3,280	2,472
Foreclosed assets held for sale	1,223	1,189
Total nonrecurring fair value measurements	4,503	3,661
Fair Value, Inputs, Level 3 [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	0	0
Fair Value, Inputs, Level 3 [Member] | Obligations of States and Political Subdivisions, Tax-exempt [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	0	0
Fair Value, Inputs, Level 3 [Member] | Obligations of States and Political Subdivisions, Taxable [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	0	0
Fair Value, Inputs, Level 3 [Member] | Collateralized Mortgage Backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	0	0
Fair Value, Inputs, Level 3 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	0	0
Fair Value, Inputs, Level 3 [Member] | Collateralized Debt Obligations [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	0	0
Fair Value, Inputs, Level 3 [Member] | Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	0	0
Fair Value, Inputs, Level 3 [Member] | Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
AVAILABLE-FOR-SALE SECURITIES:
Available-for-sale securities	$ 0	$ 0