Inventories, net (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2014	Jun. 30, 2014
Inventories, net
Raw materials	$ 65,723,000	$ 56,942,000
Work in process	22,358,000	27,462,000
Finished goods (completed systems)	15,982,000	11,385,000
Inventories, net	104,063,000	95,789,000
Inventories, net additional information
Inventory reserves	800,000			800,000	200,000
Charges to cost of sales due to below normal production capacity	1,000,000	600,000	2,600,000
Charges to cost of sales due to lower of cost or market value	800,000	700,000	500,000
Inventory reserves
Inventories, net additional information
Decrease in inventory reserves	2,452,000	10,913,000	4,819,000
Decrease in inventory reserves due to obsolescence and excess inventory	1,300,000
Reduction in reserve due to sales of previously fully reserved inventory	1,100,000
Provision charge to reserve	1,003,000	2,562,000	14,492,000
Inventory reserves	$ 23,600,000	$ 25,100,000