Note 15 - Income Taxes - Components of Income Tax Provision (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current tax expense (benefit):
Federal									$ 7,201	$ 14,509	$ 13,634
State									1,233	926	675
Total current tax expense									8,434	15,435	14,309
Deferred tax expense (benefit):
Federal									296	5,205	(1,480)
State									52	(12)	(10)
Total deferred tax expense (benefit)									348	5,193	(1,490)
Total income tax expense	$ 2,596	$ 1,118	$ 2,500	$ 2,568	$ 10,720	$ 3,894	$ 2,959	$ 3,055	$ 8,782	$ 20,628	$ 12,819