Note 8 - Deposits - Summary of Deposits (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Noninterest-bearing demand	$ 889,784,000	$ 866,380,000
Noninterest-bearing demand, percentage	36.10%	34.30%
Noninterest-bearing demand, percent increase	2.70%
Interest-bearing checking	$ 339,089,000	$ 387,758,000
Interest-bearing checking, percentage	13.80%	15.40%
Interest-bearing checking, percent increase	(12.60%)
Money market	$ 434,333,000	$ 427,119,000
Money market, percentage	17.60%	16.90%
Money market, percent increase	1.70%
Savings	$ 317,014,000	$ 327,530,000
Savings, percentage	12.90%	13.00%
Savings, percent increase	(3.20%)
Local Time, under $100,000	$ 160,092,000	$ 152,294,000
Local Time, under $100,000, percentage	6.50%	6.00%
Local Time, under $100,000, percent increase (decrease)	5.10%
Local Time, $100,000 and over	$ 210,164,000	$ 258,626,000
Local Time, $100,000 and over, percentage	8.50%	10.30%
Local Time, $100,000 and over, percent increase (decrease)	(18.70%)
Total local deposits	$ 2,350,476,000	$ 2,419,707,000
Total local deposits, percentage	95.40%	95.90%
Total local deposits, percent increase	(2.90%)
Out-of-area time, under $100,000	$ 0	$ 0
Out-of-area time, under $100,000, percentage	0.00%	0.00%
Out-of-area time, under $100,000, percent increase	0.00%
Out-of-area time, $100,000 and over	$ 113,232,000	$ 102,658,000
Out-of-area time, $100,000 and over, percentage	4.60%	4.10%
Out-of-area time, $100,000 and over, percent increase	10.30%
Total out-of-area deposits	$ 113,232,000	$ 102,658,000
Total out-of-area deposits, percentage	4.60%	4.10%
Total out-of-area deposits, percent increase	10.30%
Total deposits	$ 2,463,708,000	$ 2,522,365,000
Total deposits, percentage	100.00%	100.00%
Total deposits, percent increase	(2.30%)