Note 2 - Acquisitions (Details Textual) - USD ($) $ in Thousands			3 Months Ended
	Apr. 26, 2019	Mar. 12, 2019	Mar. 31, 2020	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2019
Payments to Acquire Businesses, Net of Cash Acquired, Total			$ (0)		$ 61,549
Goodwill, Ending Balance			$ 793,576			$ 805,284
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