Note 5 - Deposits - Summary of Deposits (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Noninterest-bearing	$ 857,734,000	$ 889,784,000
Noninterest-bearing checking, percentage	32.90%	36.10%
Noninterest-bearing checking, percent increase (decrease)	(3.60%)
Interest-bearing checking	$ 324,802,000	$ 339,089,000
Interest-bearing checking, percentage	12.40%	13.80%
Interest-bearing checking, percent increase (decrease)	(4.20%)
Money market	$ 484,035,000	$ 434,333,000
Money market, percentage	18.50%	17.60%
Money market, percent increase (decrease)	11.40%
Savings	$ 295,383,000	$ 317,014,000
Savings, percentage	11.30%	12.90%
Savings, percent increase (decrease)	(6.80%)
Local Time, under $100,000	$ 198,243,000	$ 160,092,000
Local Time, under $100,000, percentage	7.60%	6.50%
Local Time, under $100,000, percent increase (decrease)	23.80%
Local Time, $100,000 and over	$ 265,242,000	$ 210,164,000
Local Time, $100,000 and over, percentage	10.20%	8.50%
Local Time, $100,000 and over, percent increase (decrease)	26.20%
Total local deposits	$ 2,425,439,000	$ 2,350,476,000
Total local deposits, percentage	92.90%	95.40%
Total local deposits, percent increase (decrease)	3.20%
Out-of-area time, under $100,000	$ 0	$ 0
Out-of-area time, $100,000 and over	$ 185,535,000	$ 113,232,000
Out-of-area time, $100,000 and over, percentage	7.10%	4.60%
Out-of-area time, $100,000 and over, percent increase (decrease)	63.90%
Total out-of-area deposits	$ 185,535,000	$ 113,232,000
Total out-of-area deposits, percentage	7.10%	4.60%
Total out-of-area deposits, percent increase (decrease)	63.90%
Total deposits	$ 2,610,974,000	$ 2,463,708,000
Total deposits, percentage	100.00%	100.00%
Total deposits, percent increase (decrease)	6.00%