Note 5 - Deposits - Summary of Deposits (Details) - USD ($)	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Noninterest-bearing	$ 884,470,000	$ 866,380,000
Noninterest-bearing checking, percentage	35.00%	34.30%
Noninterest-bearing checking, percent increase (decrease)	2.10%
Interest-bearing checking	$ 351,184,000	$ 387,758,000
Interest-bearing checking, percentage	13.90%	15.40%
Interest-bearing checking, percent increase (decrease)	(9.40%)
Money market	$ 496,173,000	$ 427,119,000
Money market, percentage	19.60%	16.90%
Money market, percent increase (decrease)	16.20%
Savings	$ 326,782,000	$ 327,530,000
Savings, percentage	12.90%	13.00%
Savings, percent increase (decrease)	(0.20%)
Local Time, under $100,000	$ 160,131,000	$ 152,294,000
Local Time, under $100,000, percentage	6.30%	6.00%
Local Time, under $100,000, percent increase (decrease)	5.10%
Local Time, $100,000 and over	$ 223,576,000	$ 258,626,000
Local Time, $100,000 and over, percentage	8.80%	10.30%
Local Time, $100,000 and over, percent increase (decrease)	(13.60%)
Total local deposits	$ 2,442,316,000	$ 2,419,707,000
Total local deposits, percentage	96.50%	95.90%
Total local deposits, percent increase (decrease)	0.90%
Out-of-area time, under $100,000	$ 0	$ 0
Out-of-area time, $100,000 and over	$ 87,495,000	$ 102,658,000
Out-of-area time, $100,000 and over, percentage	3.50%	4.10%
Out-of-area time, $100,000 and over, percent increase (decrease)	(14.80%)
Total out-of-area deposits	$ 87,495,000	$ 102,658,000
Total out-of-area deposits, percentage	3.50%	4.10%
Total out-of-area deposits, percent increase (decrease)	(14.80%)
Total deposits	$ 2,529,811,000	$ 2,522,365,000
Total deposits, percentage	100.00%	100.00%
Total deposits, percent increase (decrease)	0.30%