Warranties Changes in accrued product warranties (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Mar. 31, 2012	Mar. 31, 2011
Movement in Standard Product Warranty Accrual [Roll Forward]
Balances at beginning of period			$ 14,719	$ 12,949	$ 14,057	$ 14,296
Increases to accruals related to sales during the period	2,650	2,498	6,350	7,542
Warranty expenditures	(1,832)	(2,073)	(6,194)	(5,770)
Balances at end of period	$ 14,875	$ 14,721	$ 14,875	$ 14,721	$ 14,057	$ 14,296