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Valuation and Qualifying Accounts (Tables)
 12 Months Ended
Dec. 31, 2017
Valuation And Qualifying Accounts [Abstract]  
Valuation and Qualifying Accounts

Allowance for Doubtful Accounts Rollforward

 

 

 

 

 

 

 

Additions

 

 

 

 

 

 

 

 

 

 

 

Balance at

 

 

Charged to

 

 

 

 

 

 

Balance at

 

 

 

Beginning

 

 

Costs and

 

 

 

 

 

 

End of

 

 

 

of Period

 

 

Expenses

 

 

Deductions(1)

 

 

Period

 

Year Ended December 31, 2017

 

$

5,805

 

 

$

10,263

 

 

$

(2,710

)

 

$

13,358

 

Year Ended December 31, 2016

 

 

5,369

 

 

 

4,160

 

 

 

(3,724

)

 

 

5,805

 

Year Ended December 31, 2015

 

 

3,002

 

 

 

3,443

 

 

 

(1,076

)

 

 

5,369

 

 

 

(1)

Uncollectible accounts written off, net of recoveries.