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Allowance for Doubtful Accounts - Summary of Allowance for Doubtful Accounts (Detail) (Allowance for Doubtful Accounts [Member], USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Allowance for Doubtful Accounts [Member]
   
Valuation and Qualifying Accounts Disclosure [Line Items]    
Balance at Beginning of Period $ 8,657 $ 11,706
Charged to Expense 4,941 4,122
Deductions (5,209) (6,984)
Balance at End of Period $ 8,389 $ 8,844