Note 5 - Deposits - Summary of Deposits (Details) - USD ($)	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Noninterest-bearing	$ 1,449,879,000	$ 924,916,000
Noninterest-bearing demand, percentage	43.00%	34.40%
Noninterest-bearing demand, percent increase	56.80%
Interest-bearing checking	$ 439,925,000	$ 332,373,000
Interest-bearing checking, percentage	13.00%	12.30%
Interest-bearing checking, percent increase (decrease)	32.40%
Money market	$ 575,077,000	$ 509,368,000
Money market, percentage	17.10%	18.90%
Money market, percent increase (decrease)	12.90%
Savings	$ 318,132,000	$ 269,318,000
Savings, percentage	9.40%	10.00%
Savings, percent increase (decrease)	18.10%
Local Time, under $100,000	$ 173,193,000	$ 198,123,000
Local Time, under $100,000, percentage	5.10%	7.40%
Local Time, under $100,000, percent increase (decrease)	(12.60%)
Local Time, $100,000 and over	$ 349,867,000	$ 322,827,000
Local Time, $100,000 and over, percentage	10.40%	12.00%
Local Time, $100,000 and over, percent increase (decrease)	8.40%
Total local deposits	$ 3,306,073,000	$ 2,556,925,000
Total local deposits, percentage	98.00%	95.00%
Total local deposits, percent increase (decrease)	29.30%
Out-of-area time, under $100,000	$ 0	$ 0
Out-of-area time, $100,000 and over	$ 65,961,000	$ 133,459,000
Out-of-area time, $100,000 and over, percentage	2.00%	5.00%
Out-of-area time, $100,000 and over, percent increase (decrease)	(50.60%)
Total out-of-area deposits	$ 65,961,000	$ 133,459,000
Total out-of-area deposits, percentage	2.00%	5.00%
Total out-of-area deposits, percent increase (decrease)	(50.60%)
Total deposits	$ 3,372,034,000	$ 2,690,384,000
Total deposits, percentage	100.00%	100.00%
Total deposits, percent increase (decrease)	25.30%