Component of Accrued Warranty Expenses (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Warranty Liability [Line Items]
Accrued warranty balance - beginning balance	$ 564	$ 469
Warranty costs incurred	(553)	(355)
Provision for warranty	524	378
Accrued warranty balance - ending balance	$ 535	$ 492