Segment Information (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 item	Jun. 30, 2012	Dec. 31, 2012
Segment Information
Number of operating segments			1
Segment information
Revenues derived from foreign subsidiaries	$ 25,352,000	$ 26,836,000	$ 50,495,000	$ 53,683,000
Identifiable assets	62,246,000		62,246,000		60,967,000
Wholly owned foreign subsidiaries
Segment information
Revenues derived from foreign subsidiaries	11,674,000	11,482,000	22,767,000	22,314,000
Identifiable assets	28,110,000	24,739,000	28,110,000	24,739,000
All subsidiaries
Segment information
Sales to customers outside of the United States	$ 11,708,000	$ 11,403,000	$ 24,013,000	$ 23,733,000