Component of Accrued Warranty Expenses (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Warranty Liability [Line Items]
Accrued warranty balance - beginning balance	$ 564	$ 469
Warranty costs incurred	(895)	(528)
Provision for warranty	1,024	538
Accrued warranty balance - ending balance	$ 693	$ 479