Note 2 - Significant Accounting Policies - Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill, balance	$ 290,191	$ 285,041
Acquisitions and adjustments		5,150
Acquisition	1,200
Goodwill, balance	$ 291,391	$ 290,191