Valuation and Qualifying Accounts (Detail) - Summarized Activity in Allowances (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Balance at Beginning of Year	$ 7,260	$ 7,200	$ 8,100
Additions Charged to Expense	1,930	930	800
Additions Charged Against Revenues	1,860	4,390	2,000
Deductions from Reserve	(4,650)	(5,260)	(3,700)
Balance at End of Year	$ 6,400	$ 7,260	$ 7,200