Summary of Depreciation Expense on Property, Plant and Equipment, Including Demo Units and Assets under Capital Leases (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Depreciation expense	$ 8,016	$ 7,400	$ 6,868