Inventories (Details) (USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Inventories
Raw materials	$ 87,938,000	$ 87,938,000		$ 85,829,000
Work in process	17,761,000	17,761,000		25,639,000
Finished goods (completed systems)	17,581,000	17,581,000		8,555,000
Inventories	123,280,000	123,280,000		120,023,000
Inventory reserves	20,200,000	20,200,000		22,800,000
Reduction in inventory due to lower than normal production capacity	$ (1,100,000)	$ 678,000	$ 661,000