Note 17 - Segment and Geographic Information - Revenue by Product Family (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue	$ 129,430	$ 128,939	$ 112,198	$ 100,362	$ 103,618	$ 106,456	$ 94,079	$ 84,512	$ 470,929	$ 388,665	$ 333,067
DC To DC Products [Member]
Revenue									431,861	350,930	299,726
Lighting Control Products [Member]
Revenue									$ 39,068	$ 37,735	$ 33,341