Segment Information (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 segment	Sep. 30, 2012	Dec. 31, 2012
Segment Information
Number of operating segments			1
Segment information
Revenues derived from foreign subsidiaries	$ 24,876,000	$ 24,316,000	$ 75,371,000	$ 77,999,000
Identifiable assets	66,991,000		66,991,000		60,967,000
Wholly owned foreign subsidiaries
Segment information
Revenues derived from foreign subsidiaries	11,167,000	9,771,000	33,934,000	32,085,000
Identifiable assets	31,480,000	25,335,000	31,480,000	25,335,000
All subsidiaries
Segment information
Sales to customers outside of the United States	$ 11,491,000	$ 10,172,000	$ 35,504,000	$ 33,905,000