Warranty Reserves and Cost Per Hour Reserves - Additional Information (Narrative) (Details) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Guarantees [Abstract]        
Standard Product Warranty Period Minimum 2 years      
Standard Product Warranty Period Maximum 5 years      
Product Warranty Expense Net $ 0 $ 0 $ (500,000)  
Cost Per Hour Expense Net 0 700,000 5,300,000  
Cost Per Hour Liability Reserve $ 0 $ 511,000 $ 3,569,000 $ 2,770,000