Note 2 - Business Segment Information - Intersegment Revenues (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	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, 2015	Sep. 30, 2015	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2014
Inter-segment Revenues	$ 83,409	$ 78,843	$ 92,305	$ 87,466	$ 83,419	$ 78,156	$ 85,658	$ 84,159	$ 80,844	$ 70,740	$ 84,687	$ 85,925	$ 342,023	$ 331,392	$ 322,196	$ 307,857	$ 299,463
Lighting Segment [Member]
Inter-segment Revenues													260,613	258,997	244,228
Graphics Segment [Member]
Inter-segment Revenues													81,410	72,395	77,968
Intersegment Eliminations [Member] | Lighting Segment [Member]
Inter-segment Revenues													2,672	2,499	2,771
Intersegment Eliminations [Member] | Graphics Segment [Member]
Inter-segment Revenues													$ 1,276	$ 1,135	$ 1,760