Inventories (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Inventory Disclosure [Abstract]
Raw materials and assembled parts	$ 68,105	$ 57,043
Service inventories, estimated current requirements	13,978	11,581
Work-in-process	66,275	55,279
Finished goods	33,652	32,061
Total current inventories	182,010	155,964
Non-current inventories	$ 57,575	$ 47,976