Note 3 - Acquisitions (Details Textual) - USD ($) $ in Thousands				3 Months Ended	12 Months Ended
	Apr. 26, 2019	Mar. 12, 2019	Jun. 01, 2018	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Payments to Acquire Businesses, Net of Cash Acquired, Total					$ 112,001	$ 65,440	$ (1,257)
Goodwill, Ending Balance					805,284	$ 764,655	$ 721,523
Pika [Member]
Payments to Acquire Businesses, Net of Cash Acquired, Total	$ 49,068
Business Acquisition, Purchase Price Allocation, Intangible Assets Including Goodwill	58,196
Goodwill, Ending Balance	$ 19,896
Neurio [Member]
Payments to Acquire Businesses, Net of Cash Acquired, Total		$ 59,071		$ 7,922
Business Acquisition, Purchase Price Allocation, Intangible Assets Including Goodwill		58,762
Goodwill, Ending Balance		$ 17,862
Selmec [Member]
Payments to Acquire Businesses, Net of Cash Acquired, Total			$ 79,972
Goodwill, Ending Balance			46,196
Business Combination, Liabilities Arising from Contingencies, Amount Recognized			$ 14,902
Business Combination, Liabilities Arising from Contingencies, Changes in Fair Value					(977)
Business Combination, Liabilities Arising from Contingencies, Interest Accretion					2,740
Business Combination, Liabilities Arising from Contingencies, Other Fair Value Re-measurement Adjustments					$ (3,717)