Note 7 - Credit Losses (Details Textual) - USD ($) $ in Thousands	Jan. 01, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance		$ 553,519	$ 572,395	$ 551,611	$ 343,641
Cumulative Effect, Period of Adoption, Adjustment [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance			(3,298)
Retained Earnings [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance		$ 246,850	259,903	$ 182,148	$ (43,713)
Retained Earnings [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance	$ 3,298		$ (3,298)
Income Tax Effects Allocated Directly to Equity, Cumulative Effect of Change in Accounting Principle	$ 1,109