Inventories (Details) (USD $)	Jun. 30, 2012	Dec. 31, 2011
Inventories
Raw materials	$ 85,576,000	$ 85,829,000
Work in process	28,712,000	25,639,000
Finished goods (completed systems)	12,359,000	8,555,000
Inventories	126,647,000	120,023,000
Inventory reserves	$ 21,500,000	$ 22,800,000