Note 8 - Accrued Retirement Benefits (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Pension Plan [Member]
Accrued retirement benefits	$ 6,268	$ 6,264
Supplemental Employee Retirement Plan [Member]
Accrued retirement benefits	4,164	4,154
Deferred Compensation Plan [Member]
Accrued retirement benefits	195	212
Accrued retirement benefits	10,627	10,630
Less current portion	378	378
Non-current portion of accrued retirement benefits	$ 10,249	$ 10,252