Note 1 - Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Notes Tables

Schedule of Deferred Compensation Plan [Table Text Block]

	December 31,
	2017		2016
Deferred compensation plan asset components:
Cash surrender value of corporate-owned life insurance policies	$	11,455	$	8,180
Fair value of mutual funds		16,625		12,108
Total	$	28,080	$	20,288
Deferred compensation plan assets reported in:
Other long-term assets	$	28,080	$	20,288
Deferred compensation plan liabilities reported in:
Accrued compensation and related benefits (short-term)	$	356	$	479
Other long-term liabilities		28,087		19,836
Total	$	28,443	$	20,315