Guarantees (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Movement in Standard Product Warranty Accrual [Roll Forward]
Standard warranty period	1 year
Beginning balance	$ 2,422	$ 3,636	$ 3,618
Provision for warranties	3,492	3,061	4,163
Claims made	(3,628)	(4,275)	(4,145)
Ending balance	$ 2,286	$ 2,422	$ 3,636