17. Quarterly results of operations (unaudited) (Details) - Quarter Ended (In thousands, except per share amounts) March 31 June 30 September 30 D (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
2013:
Net sales	$ 12,296	$ 13,389	$ 13,804	$ 13,619	$ 12,528	$ 16,768	$ 15,788	$ 15,057	$ 53,108	$ 60,141	$ 68,386
Gross profit	4,911	5,286	5,788	5,726	5,001	7,206	6,452	6,433	21,711	25,092	25,982
Net income	$ (3,040)	$ 50	$ 175	$ 394	$ 1,109	$ 1,451	$ 1,215	$ 1,160	$ (2,421)	$ 4,935	$ 3,621
Net income per share:
Basic (in Dollars per share)	$ (0.37)	$ 0.01	$ 0.02	$ 0.05	$ 0.13	$ 0.17	$ 0.14	$ 0.13	$ (0.29)	$ 0.57	$ 0.40
Diluted (in Dollars per share)	$ (0.37)	$ 0.01	$ 0.02	$ 0.05	$ 0.13	$ 0.17	$ 0.14	$ 0.13	$ (0.29)	$ 0.57	$ 0.40