Product Warranty Reserves (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Product warranty reserves [Roll Forward]
Reserve balance, beginning of year	$ 9,891	$ 8,714	$ 10,050
Provision for warranty	13,029	13,365	10,908
Warranty liabilities settled	(10,567)	(12,270)	(12,416)
Other	310	82	172
Reserve balance, end of year	$ 12,663	$ 9,891	$ 8,714