Note 5 - Deposits - Summary of Deposits (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Noninterest-bearing demand	$ 830,187,000	$ 866,380,000
Noninterest-bearing demand	32.70%	34.30%
Noninterest-bearing demand	(4.20%)
Interest-bearing checking	$ 392,134,000	$ 387,758,000
Interest-bearing checking	15.40%	15.40%
Interest-bearing checking	1.10%
Money market	$ 486,318,000	$ 427,119,000
Money market	19.10%	16.90%
Money market	13.90%
Savings	$ 326,247,000	$ 327,530,000
Savings	12.90%	13.00%
Savings	(0.40%)
Local Time, under $100,000	$ 156,053,000	$ 152,294,000
Local Time, under $100,000	6.20%	6.00%
Local Time, under $100,000	2.50%
Local Time, $100,000 and over	$ 246,703,000	$ 258,626,000
Local Time, $100,000 and over	9.70%	10.30%
Local Time, $100,000 and over	(4.60%)
Total local deposits	$ 2,437,642,000	$ 2,419,707,000
Total local deposits	96.00%	95.90%
Total local deposits	0.70%
Out-of-area time, under $100,000	$ 0	$ 0
Out-of-area time, $100,000 and over	$ 102,411,000	$ 102,658,000
Out-of-area time, $100,000 and over	4.00%	4.10%
Out-of-area time, $100,000 and over	(0.20%)
Total out-of-area deposits	$ 102,411,000	$ 102,658,000
Total out-of-area deposits	4.00%	4.10%
Total out-of-area deposits	(0.20%)
Deposits, Total	$ 2,540,053,000	$ 2,522,365,000
Total deposits	100.00%	100.00%
Aggregate Increase (Decrease) in Percentage of Deposits	0.70%