Note 7 - Deposits - Summary of Deposits (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Noninterest-bearing checking	$ 1,433,403,000	$ 924,916,000
Noninterest-bearing checking, percentage	42.00%	34.40%
Noninterest-bearing checking, percent increase (decrease)	55.00%
Interest-bearing checking	$ 473,053,000	$ 332,373,000
Interest-bearing checking, percentage	13.90%	12.30%
Interest-bearing checking, percent increase (decrease)	42.30%
Money market	$ 611,912,000	$ 509,368,000
Money market, percentage	17.90%	18.90%
Money market, percent increase (decrease)	20.10%
Savings	$ 338,070,000	$ 269,318,000
Savings, percentage	9.90%	10.00%
Savings, percent increase (decrease)	25.50%
Local Time, under $100,000	$ 165,548,000	$ 198,123,000
Local Time, under $100,000, percentage	4.90%	7.40%
Local Time, under $100,000, percent increase (decrease)	(16.40%)
Local Time, $100,000 and over	$ 342,633,000	$ 322,827,000
Local Time, $100,000 and over, percentage	10.00%	12.00%
Local Time, $100,000 and over, percent increase (decrease)	6.10%
Total local deposits	$ 3,364,619,000	$ 2,556,925,000
Total local deposits, percentage	98.60%	95.00%
Total local deposits, percent increase (decrease)	31.60%
Out-of-area time, $100,000 and over	$ 46,934,000	$ 133,459,000
Out-of-area time, $100,000 and over, percentage	1.40%	5.00%
Out-of-area time, $100,000 and over, percent increase (decrease)	(64.80%)
Total deposits	$ 3,411,553,000	$ 2,690,384,000
Total deposits, percentage	100.00%	100.00%
Total deposits, percent increase (decrease)	26.80%