Property, Plant and Equipment (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Property, Plant and Equipment, Net, by Type [Abstract]
Land	$ 7,780	$ 7,780
Buildings and improvements	21,478	21,216
Leasehold improvements	11,296	9,616
Machinery and equipment	81,046	79,901
Demonstration systems	29,899	26,208
Other fixed assets	40,343	31,680
Gross property, plant and equipment	191,842	176,401
Accumulated depreciation	(106,760)	(95,720)
Total property, plant and equipment, net	$ 85,082	$ 80,681