Note 5 - Deposits - Summary of Deposits (Details) - USD ($)	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Noninterest-bearing	$ 879,442,000	$ 866,380,000
Noninterest-bearing checking, percentage	35.10%	34.30%
Noninterest-bearing checking, percent increase (decrease)	1.50%
Interest-bearing checking	$ 350,056,000	$ 387,758,000
Interest-bearing checking, percentage	14.00%	15.40%
Interest-bearing checking, percent increase (decrease)	(9.70%)
Money market	$ 504,741,000	$ 427,119,000
Money market, percentage	20.10%	16.90%
Money market, percent increase (decrease)	18.20%
Savings	$ 311,566,000	$ 327,530,000
Savings, percentage	12.40%	13.00%
Savings, percent increase (decrease)	(4.90%)
Local Time, under $100,000	$ 162,074,000	$ 152,294,000
Local Time, under $100,000, percentage	6.50%	6.00%
Local Time, under $100,000, percent increase (decrease)	6.40%
Local Time, $100,000 and over	$ 219,713,000	$ 258,626,000
Local Time, $100,000 and over, percentage	8.70%	10.30%
Local Time, $100,000 and over, percent increase (decrease)	(15.00%)
Total local deposits	$ 2,427,592,000	$ 2,419,707,000
Total local deposits, percentage	96.80%	95.90%
Total local deposits, percent increase (decrease)	0.30%
Out-of-area time, under $100,000	$ 0	$ 0
Out-of-area time, $100,000 and over	$ 81,218,000	$ 102,658,000
Out-of-area time, $100,000 and over, percentage	3.20%	4.10%
Out-of-area time, $100,000 and over, percent increase (decrease)	(20.90%)
Total out-of-area deposits	$ 81,218,000	$ 102,658,000
Total out-of-area deposits, percentage	3.20%	4.10%
Total out-of-area deposits, percent increase (decrease)	(20.90%)
Total deposits	$ 2,508,810,000	$ 2,522,365,000
Total deposits, percentage	100.00%	100.00%
Total deposits, percent increase (decrease)	(0.50%)