Note 1 - Summary of Significant Accounting Policies - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash payments:
Income tax payments	$ 15,838	$ 12,860	$ 13,831
Cash paid for interest	7,158	4,901	4,856
Non-cash transactions:
Transfers from loans to other real estate owned		$ 1,916	$ 1,146