Note 5 - Deposits - Summary of Deposits (Details) - USD ($)	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Noninterest-bearing	$ 967,189,000	$ 889,784,000
Noninterest-bearing checking, percentage	35.00%	36.10%
Noninterest-bearing checking, percent increase (decrease)	8.70%
Interest-bearing checking	$ 327,679,000	$ 339,089,000
Interest-bearing checking, percentage	11.80%	13.80%
Interest-bearing checking, percent increase (decrease)	(3.40%)
Money market	$ 522,742,000	$ 434,333,000
Money market, percentage	18.90%	17.60%
Money market, percent increase (decrease)	20.40%
Savings	$ 269,958,000	$ 317,014,000
Savings, percentage	9.80%	12.90%
Savings, percent increase (decrease)	(14.80%)
Local Time, under $100,000	$ 204,767,000	$ 160,092,000
Local Time, under $100,000, percentage	7.40%	6.50%
Local Time, under $100,000, percent increase (decrease)	27.90%
Local Time, $100,000 and over	$ 321,311,000	$ 210,164,000
Local Time, $100,000 and over, percentage	11.60%	8.50%
Local Time, $100,000 and over, percent increase (decrease)	52.90%
Total local deposits	$ 2,613,646,000	$ 2,350,476,000
Total local deposits, percentage	94.50%	95.40%
Total local deposits, percent increase (decrease)	11.20%
Out-of-area time, under $100,000	$ 0	$ 0
Out-of-area time, under $100,000, percentage
Out-of-area time, under $100,000, percent increase (decrease)
Out-of-area time, $100,000 and over	$ 153,445,000	$ 113,232,000
Out-of-area time, $100,000 and over, percentage	5.50%	4.60%
Out-of-area time, $100,000 and over, percent increase (decrease)	35.50%
Total out-of-area deposits	$ 153,445,000	$ 113,232,000
Total out-of-area deposits, percentage	5.50%	4.60%
Total out-of-area deposits, percent increase (decrease)	35.50%
Total deposits	$ 2,767,091,000	$ 2,463,708,000
Total deposits, percentage	100.00%	100.00%
Total deposits, percent increase (decrease)	12.30%