Note 6 - Accrued Retirement Benefits - Accrued Retirement Benefits (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accrued retirement benefits	$ 9,234	$ 10,630
Accrued retirement benefits	9,234	10,630
Less current portion	(175)	(378)
Non-current portion of accrued retirement benefits	9,059	10,252
Pension Plan [Member]
Accrued retirement benefits	7,560	6,264
Accrued retirement benefits	7,560	6,264
Supplemental Employee Retirement Plan [Member]
Accrued retirement benefits	1,674	4,366
Accrued retirement benefits	$ 1,674	$ 4,366