Note 5 - Deposits - Summary of Deposits (Details) - USD ($)	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Noninterest-bearing checking	$ 1,686,203,000	$ 1,677,952,000
Noninterest-bearing checking, percentage	42.40%	41.10%
Noninterest-bearing checking, percent increase (decrease)	0.50%
Interest-bearing checking	$ 544,221,000	$ 538,838,000
Interest-bearing checking, percentage	13.70%	13.20%
Interest-bearing checking, percent increase (decrease)	1.00%
Money market	$ 943,246,000	$ 1,040,176,000
Money market, percentage	23.70%	25.50%
Money market, percent increase (decrease)	(9.30%)
Savings	$ 406,545,000	$ 394,330,000
Savings, percentage	10.20%	9.70%
Savings, percent increase (decrease)	3.10%
Local Time, under $100,000	$ 127,755,000	$ 132,776,000
Local Time, under $100,000, percentage	3.20%	3.20%
Local Time, under $100,000, percent increase (decrease)	(3.80%)
Local Time, $100,000 and over	$ 252,088,000	$ 275,208,000
Local Time, $100,000 and over, percentage	6.40%	6.70%
Local Time, $100,000 and over, percent increase (decrease)	(8.40%)
Total local deposits	$ 3,960,058,000	$ 4,059,280,000
Total local deposits, percentage	99.60%	99.40%
Total local deposits, percent increase (decrease)	(2.40%)
Out-of-area time, $100,000 and over	$ 16,193,000	$ 23,913,000
Out-of-area time, $100,000 and over, percentage	0.40%	0.60%
Out-of-area time, $100,000 and over, percent increase (decrease)	(32.30%)
Total deposits	$ 3,976,251,000	$ 4,083,193,000
Total deposits, percentage	100.00%	100.00%
Total deposits, percent increase (decrease)	(2.60%)