Note 8 - Deposits - Summary of Deposits (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Noninterest-bearing	$ 924,916,000	$ 889,784,000
Noninterest-bearing demand, percentage	34.40%	36.10%
Noninterest-bearing demand, percent increase	3.90%
Interest-bearing checking	$ 332,373,000	$ 339,089,000
Interest-bearing checking, percentage	12.30%	13.80%
Interest-bearing checking, percent increase (decrease)	(2.00%)
Money market	$ 509,368,000	$ 434,333,000
Money market, percentage	18.90%	17.60%
Money market, percent increase (decrease)	17.30%
Savings	$ 269,318,000	$ 317,014,000
Savings, percentage	10.00%	12.90%
Savings, percent increase (decrease)	(15.00%)
Local Time, under $100,000	$ 198,123,000	$ 160,092,000
Local Time, under $100,000, percentage	7.40%	6.50%
Local Time, under $100,000, percent increase (decrease)	23.80%
Local Time, $100,000 and over	$ 322,827,000	$ 210,164,000
Local Time, $100,000 and over, percentage	12.00%	8.50%
Local Time, $100,000 and over, percent increase (decrease)	53.60%
Total local deposits	$ 2,556,925,000	$ 2,350,476,000
Total local deposits, percentage	95.00%	95.40%
Total local deposits, percent increase (decrease)	8.80%
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 (decrease)	0.00%
Out-of-area time, $100,000 and over	$ 133,459,000	$ 113,232,000
Out-of-area time, $100,000 and over, percentage	5.00%	4.60%
Out-of-area time, $100,000 and over, percent increase (decrease)	17.90%
Total out-of-area deposits	$ 133,459,000	$ 113,232,000
Total out-of-area deposits, percentage	5.00%	4.60%
Total out-of-area deposits, percent increase (decrease)	17.90%
Total deposits	$ 2,690,384,000	$ 2,463,708,000
Total deposits, percentage	100.00%	100.00%
Total deposits, percent increase (decrease)	9.20%