Transactions in the Allowance for Doubtful Accounts (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance, beginning of year	$ 31,328	$ 30,945	$ 30,651
Provision	10,459	9,052	13,922
Write-offs	(7,227)	(8,669)	(13,628)
Balance, end of year	$ 34,560	$ 31,328	$ 30,945