Valuation and Qualifying Accounts (Detail) (Allowance for Doubtful Accounts, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Allowance for Doubtful Accounts
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 6,165	[1]	$ 3,917	[1]	$ 519	[1]
Additions Charged to Costs and Expenses	467	[1]	2,253	[1]	4,312	[1]
Deductions			(5)	[1]	(914)	[1]
Balance at End of Period	$ 6,632	[1]	$ 6,165	[1]	$ 3,917	[1]

[1] These amounts include reserves for bad debts.