Acquisitions (Details Textual) (USD $)	12 Months Ended			3 Months Ended	1 Months Ended	3 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Mar. 30, 2012 Aerospace Metal Composites Limited [Member]	Oct. 31, 2011 EIS Optics Limited [Member] sqft	Mar. 30, 2012 EIS Optics Limited [Member]	Jul. 02, 2010 Academy Corporation [Member]	Jan. 31, 2010 Academy Corporation [Member]
Acquisitions (Textual) [Abstract]
Payments to acquire business, net of cash acquired	$ 3,894,000	$ 22,448,000	$ 20,605,000	$ 3,300,000
Cash acquired from acquisition				1,500,000
Goodwill	88,753,000	84,036,000	72,936,000	1,900,000
Acquistions for cash					24,500,000			21,000,000
Area for manufacturing facility in shanghai, China					101,000
Payments as a result of the resolution of working capital valuation adjustments						600,000
Preliminary goodwill assigned					13,900,000			5,400,000
Cash received from seller							$ 1,700,000