Activity In Allowance For Doubtful 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 Allowance [Line Items]
Balance at beginning of period	$ 2,893	$ 1,544	$ 2,083
Charged to expense	200	4,868	350
Write-offs, net of recoveries	(745)	(3,519)	(889)
Balance at end of period	$ 2,348	$ 2,893	$ 1,544