Note 15 - Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued expenses	$ 21,053	$ 16,745
Deferred revenue	14,697	12,418
Inventories	9,879	8,500
Pension obligations	0	1,062
Stock-based compensation	7,490	5,960
Operating loss and credit carryforwards	28,356	25,585
Bad debt	1,094	1,363
Other	4,275	2,516
Valuation allowance	(5,024)	(5,802)
Total deferred tax assets	81,820	68,347
Goodwill and intangible assets	142,159	108,899
Depreciation	27,864	25,429
Debt refinancing costs	4,119	4,206
Prepaid expenses	1,073	950
Total deferred tax liabilities	175,215	139,484
Net deferred tax liabilities	$ (93,395)	$ (71,137)