Note 2 - Acquisition of Community State Bank and Common Stock Offering - Pro Forma Combined Operating Results (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Net interest income	$ 110,035	$ 98,483
Noninterest income	34,773	31,051
Net income	$ 34,137	$ 22,118
Earnings per common share:
Basic (in dollars per share)	$ 2.62	$ 1.91
Diluted (in dollars per share)	$ 2.58	$ 1.89