Accrued Warranty Costs - Changes in Product Warranty Obligation (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accrued Warranty Costs [Line Items]
Balance at beginning of year	$ 5,370	$ 3,996	$ 3,138
Amounts charged to costs and expenses	6,710	6,539	4,479
Costs incurred	(5,908)	(5,165)	(3,621)
Balance at end of year	$ 6,172	$ 5,370	$ 3,996