Note 7 - Income Tax Expense - Deferred Income Tax Asset (Liability) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred income tax assets:
Pension accruals	$ 2,588	$ 2,729
Operating reserves and other accruals	2,540	1,984
Tax credits	923	748
Valuation allowance on tax credits	(923)	(748)
Deferred income tax liabilities:
Book carrying value in excess of tax basis of property	(1,544)	(1,495)
Book carrying value in excess of tax basis of intangibles	(7,024)	(6,906)
Tax effect of revenue recognition standard ASC 606	(1,771)	(2,657)
Deferred expenses	(1,831)	(2,130)
Net deferred income tax liability	$ (7,042)	$ (8,475)