Component of Accrued Warranty Expenses (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Warranty Liability [Line Items]
Accrued warranty beginning balance	$ 690	$ 564
Warranty costs incurred	(854)	(895)
Provision for warranty expense	926	1,024
Accrued warranty ending balance	$ 762	$ 693