Note 6 - Goodwill and Other Intangible Assets - Goodwill (Details) - USD ($)	3 Months Ended		6 Months Ended
	Dec. 31, 2018	Sep. 30, 2017	Dec. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Goodwill				$ 123,254,000	$ 123,254,000
Accumulated impairment losses				(112,881,000)	(92,716,000)
Goodwill, net				10,373,000	30,538,000
Goodwill impairment			$ (20,165,000)
Lighting Segment [Member]
Goodwill				94,564,000	94,564,000
Accumulated impairment losses				(85,356,000)	(65,191,000)
Goodwill, net				9,208,000	29,373,000
Goodwill impairment	$ (20,165,000)	$ (28,000,000)	(20,165,000)
Graphics Segment [Member]
Goodwill				28,690,000	28,690,000
Accumulated impairment losses				(27,525,000)	(27,525,000)
Goodwill, net				$ 1,165,000	$ 1,165,000
Goodwill impairment