Guarantees (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Movement in Standard Product Warranty Accrual [Roll Forward]
Standard warranty period	1 year
Beginning balance	$ 3,618	$ 3,363	$ 3,383
Provision for warranties	4,163	4,344	3,510
Claims made	(4,145)	(4,089)	(3,530)
Ending balance	$ 3,636	$ 3,618	$ 3,363