Valuation and Qualifying Accounts (Detail) - Allowance for Doubtful Accounts (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Beginning Balance	$ 2,662	$ 815	$ 432
Charged to Costs and Expenses	2,852	2,297	173
Deductions	(1,370)	(450)	(109)
Acquisitions	215		319
Ending Balance	$ 4,359	$ 2,662	$ 815