Note 13 - Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accrued expenses	$ 16,745	$ 15,075
Deferred revenue	12,418	9,983
Inventories	8,500	7,933
Pension obligations	1,062	3,795
Stock-based compensation	5,960	5,522
Operating loss and credit carryforwards	25,585	23,771
Bad debt	1,363	1,101
Other	2,516	40
Valuation allowance	(5,802)	(6,817)
Total deferred tax assets	68,347	60,403
Goodwill and intangible assets	108,899	70,556
Depreciation	25,429	22,563
Debt refinancing costs	4,206	5,189
Prepaid expenses	950	709
Total deferred tax liabilities	139,484	99,017
Net deferred tax liabilities	$ (71,137)	$ (38,614)