Note 11 - Segment Reporting - Income From Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income from operations	$ 19,367	$ 16,942	$ 53,451	$ 46,936
Operating Segments [Member] | United States Segment [Member]
Income from operations	26,903	23,910	76,973	67,542
Operating Segments [Member] | Europe Segment [Member]
Income from operations	3,251	3,554	9,626	9,369
Corporate and Reconciling Items [Member] | Corporate Unallocated and Japan Segment[Member]
Income from operations	$ (10,787)	$ (10,522)	$ (33,148)	$ (29,975)