Valuation and Qualifying Accounts (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Allowance for Doubtful Trade Accounts Receivable
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	$ 4,615	$ 4,708	$ 4,708
Addition charged to expenses	2,235	2,234	1,375
Write-offs, net of recoveries	(1,994)	(2,327)	(1,375)
Balance at end of year	4,856	4,615	4,708
Deferred Tax Asset Valuation Allowance
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	1,262	163	332
Addition charged to expenses		1,099
Deferred tax assets adjusted or utilized	(340)		(169)
Balance at end of year	$ 922	$ 1,262	$ 163