Valuation and Qualifying Accounts (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 12,113		$ 7,593		$ 9,887
Charged to Costs and Expenses	4,024		10,138		5,732
Deductions	9,210	[1]	5,618	[1]	8,026	[1]
Balance at End of Period	$ 6,927		$ 12,113		$ 7,593

[1] Accounts deemed to be uncollectible.