Note 10 - Deferred Compensation Plan - Summary of Deferred Compensation Plan (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Deferred compensation plan assets	$ 24,315	$ 20,288
Deferred compensation plan liabilities	24,487	20,315
Other Long-term Assets [Member]
Deferred compensation plan assets	24,315	20,288
Accrued Compensation and Related Benefits [Member]
Deferred compensation plan liabilities	341	479
Other Long-term Liabilities [Member]
Deferred compensation plan liabilities	24,146	19,836
Cash Surrender Value [Member]
Deferred compensation plan assets	11,218	8,180
Mutual Funds, Fair Value [Member]
Deferred compensation plan assets	$ 13,097	$ 12,108