Inventories - Changes in Inventory Reserves (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Inventory Disclosure [Line Items]
Balance at beginning of year	$ 1,783	$ 1,793	$ 1,676
Provisions for losses	1,140	590	184
Write-offs and disposals	(130)	(600)	(67)
Balance at end of year	$ 2,793	$ 1,783	$ 1,793