9. Industry Segment and Geographic Information (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
Segment Reporting Information [Line Items]
Revenues	$ 34,024	$ 37,903	$ 36,164	$ 38,504	$ 33,294	$ 37,835	$ 36,143	$ 36,215	$ 146,595	$ 143,487	$ 145,733
U S
Segment Reporting Information [Line Items]
Revenues									93,082	91,092	94,840
Canada
Segment Reporting Information [Line Items]
Revenues									8,172	6,396	7,156
Other Countries [Member]
Segment Reporting Information [Line Items]
Revenues									$ 45,341	$ 45,999	$ 43,737