Note 5 - Deposits - Summary of Deposits (Details) - USD ($)	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Noninterest-bearing	$ 1,647,380,000	$ 1,433,403,000
Noninterest-bearing checking, percentage	42.60%	42.00%
Noninterest-bearing checking, percent increase (decrease)	14.90%
Interest-bearing checking	$ 535,983,000	$ 473,053,000
Interest-bearing checking, percentage	13.90%	13.90%
Interest-bearing checking, percent increase (decrease)	13.30%
Money market	$ 854,763,000	$ 611,912,000
Money market, percentage	22.10%	17.90%
Money market, percent increase (decrease)	39.70%
Savings	$ 392,298,000	$ 338,070,000
Savings, percentage	10.10%	9.90%
Savings, percent increase (decrease)	16.00%
Local Time, under $100,000	$ 139,031,000	$ 165,548,000
Local Time, under $100,000, percentage	3.60%	4.90%
Local Time, under $100,000, percent increase (decrease)	(16.00%)
Local Time, $100,000 and over	$ 275,623,000	$ 342,633,000
Local Time, $100,000 and over, percentage	7.10%	10.00%
Local Time, $100,000 and over, percent increase (decrease)	(19.60%)
Total local deposits	$ 3,845,078,000	$ 3,364,619,000
Total local deposits, percentage	99.40%	98.60%
Total local deposits, percent increase (decrease)	14.30%
Out-of-area time, $100,000 and over	$ 23,913,000	$ 46,934,000
Out-of-area time, $100,000 and over, percentage	0.60%	1.40%
Out-of-area time, $100,000 and over, percent increase (decrease)	(49.00%)
Total deposits	$ 3,868,991,000	$ 3,411,553,000
Total deposits, percentage	100.00%	100.00%
Total deposits, percent increase (decrease)	13.40%