Note 11 - Segment Reporting - Income From Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income from operations	$ 16,402	$ 14,851	$ 34,084	$ 29,994
Operating Segments [Member] | United States Segment [Member]
Income from operations	25,723	21,528	50,069	43,632
Operating Segments [Member] | Europe Segment [Member]
Income from operations	2,335	3,431	6,375	5,815
Corporate and Reconciling Items [Member] | Corporate Unallocated and Japan Segment[Member]
Income from operations	$ (11,656)	$ (10,108)	$ (22,360)	$ (19,453)