Note 5 - Deposits - Summary of Deposits (Details) - USD ($)	9 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Noninterest-bearing demand	$ 1,716,904,000	$ 1,677,952,000
Noninterest-bearing demand, percentage	44.60%	41.10%
Noninterest-bearing demand, percent increase (decrease)	2.30%
Interest-bearing checking	$ 529,297,000	$ 538,838,000
Interest-bearing checking, percentage	13.80%	13.20%
Interest-bearing checking, percent increase (decrease)	(1.80%)
Money market	$ 808,734,000	$ 1,040,176,000
Money market, percentage	21.00%	25.50%
Money market, percent increase (decrease)	(22.30%)
Savings	$ 412,491,000	$ 394,330,000
Savings, percentage	10.70%	9.70%
Savings, percent increase (decrease)	4.60%
Local Time, under $100,000	$ 114,751,000	$ 132,776,000
Local Time, under $100,000, percentage	3.00%	3.20%
Local Time, under $100,000, percent increase (decrease)	(13.60%)
Local Time, $100,000 and over	$ 263,908,000	$ 275,208,000
Local Time, $100,000 and over, percentage	6.90%	6.70%
Local Time, $100,000 and over, percent increase (decrease)	(4.10%)
Total local deposits	$ 3,846,085,000	$ 4,059,280,000
Total local deposits, percentage	100.00%	99.40%
Total local deposits, percent increase (decrease)	(5.30%)
Out-of-area time, $100,000 and over	$ 0	$ 23,913,000
Out-of-area time, $100,000 and over, percentage	0.00%	0.60%
Total deposits	$ 3,846,085,000	$ 4,083,193,000
Total deposits, percentage	100.00%	100.00%
Total deposits, percent increase (decrease)	(5.80%)