Valuation and Qualifying Accounts (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at the beginning of the year	$ 616	$ 716	$ 590
Charged to costs and expenses	255	(7)	293
Charged to other accounts			(39)
Write-offs	(180)	(93)	(128)
Balance at the end of the year	$ 691	$ 616	$ 716