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 Beginning of Period	$ 9,300	$ 10,026	$ 10,303
Additions Charged to Cost and Expense	2,554	2,069	2,198
Deductions Bad Debt Write-offs	(2,928)	(2,795)	(2,475)
Balance at End of Period	$ 8,926	$ 9,300	$ 10,026