Warranty Contracts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Warranty Contracts [Line Items]
Product Warranty Period	1 year
Beginning Balance Deferred Warranty Revenue	$ 10,663	$ 11,914	$ 9,141
Warranty Revenue Deferred	12,859	15,349	17,185
Warranty Revenue Recognized	(14,471)	(16,600)	(14,412)
Ending Balance Deferred Warranty Revenue	9,051	10,663	11,914
Warranty Costs Incurred	13,713	11,761	11,398
Materials [Member]
Warranty Contracts [Line Items]
Warranty Costs Incurred	6,851	6,202	5,958
Labor And Overhead [Member]
Warranty Contracts [Line Items]
Warranty Costs Incurred	$ 6,862	$ 5,559	$ 5,440