Warranty Accrual - Additional Information (Detail) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Product Liability Contingency [Line Items]
Offset included in cash payments		$ 1,300,000
Adjustments to warranty reserve	$ 1.8		$ 2.3