Note 6 - Accrued Retirement Benefits - Accrued Retirement Benefits (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Pension Plan [Member]
Accrued retirement benefits	$ 6,264	$ 2,540
Supplemental Employee Retirement Plan [Member]
Accrued retirement benefits	4,154	4,468
Deferred Compensation Plan [Member]
Accrued retirement benefits	212	276
Accrued retirement benefits	10,630	7,284
Less current portion	378	391
Non-current portion of accrued retirement benefits	$ 10,252	$ 6,893