Supplementary Financial Information to Item 8. (Details) - USD ($) $ / shares in Units, $ 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
Quarterly Financial Information Disclosure [Abstract]
Net sales from continuing operations	$ 4,727	$ 5,002	$ 6,011	$ 4,106	$ 7,186	$ 8,261	$ 7,126	$ 8,425	$ 19,846	$ 30,998	$ 64,403
Gross profit from continuing operations	1,622	1,137	1,501	561	(1,072)	3,082	2,522	3,145	4,821	7,677	29,292
Net loss from continuing operations	(1,858)	(1,773)	(3,114)	(4,522)	(7,805)	(3,177)	(3,916)	(1,977)	(11,267)	(16,875)	9,471
Loss from discontinued operations	0	0	0	0	0	0	0	(12)	0	(12)	(691)
Net (loss) income	$ (1,858)	$ (1,773)	$ (3,114)	$ (4,522)	$ (7,805)	$ (3,177)	$ (3,916)	$ (1,989)	$ (11,267)	$ (16,887)	$ 8,780
Denominator:
Net (loss) income from continuing operations (in dollars per share)	$ (0.16)	$ (0.15)	$ (0.26)	$ (0.39)
Net loss from discontinued operations (in dollars per share)	0.00	0.00	0.00	0.00
Net loss (in dollars per share)	$ (0.16)	$ (0.15)	$ (0.26)	$ (0.39)
Net (loss) income per share - basic:
Net income (loss) from continuing operations (in dollars per share)					$ (0.67)	$ (0.27)	$ (0.34)	$ (0.17)	$ (0.95)	$ (1.45)	$ 0.91
Net (loss) income from discontinued operations (in dollars per share)					0.00	0.00	0.00	0.00	0.00	0.00	(0.07)
Net income (loss) (in dollars per share)					$ (0.67)	$ (0.27)	$ (0.34)	$ (0.17)	(0.95)	(1.45)	0.84
Income (loss) from continuing operations
Net income (loss) from continuing operations (in dollars per share)									(0.95)	(1.45)	0.88
Net (loss) income from discontinued operations (in dollars per share)									0.00	0.00	(0.06)
Net income (loss) (in dollars per share)									$ (0.95)	$ (1.45)	$ 0.82