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Allowance for Doubtful Accounts
 3 Months Ended
Mar. 31, 2018
Receivables [Abstract]  
Allowance for Doubtful Accounts

5. Allowance for Doubtful Accounts

 

     Balance at
Beginning of
Period		      Charged to
Expense		      Deductions(1)      Balance at
End of
Period		  

Three months ended March 31, 2018

    $ 5,907        4,997        (3,722 )     $ 7,182  

Three months ended March 31, 2017

    $ 5,918        4,383        (3,382 )     $ 6,919  

 

(1) Deductions represent accounts written off, net of recoveries.