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Accounts Receivable - Additional Information (Details) - USD ($)
$ in Millions
9 Months Ended 12 Months Ended
Sep. 30, 2018
Dec. 31, 2017
Concentration Risk [Line Items]    
Trade receivable payments terms (30 days or less) 30 days  
Threshold period past due for write-off of trade accounts receivable 150 days  
Revolving line-of-credit facility under 2016 Credit Agreement    
Concentration Risk [Line Items]    
Receivables with revolving credit balances $ 19.5 $ 12.2
29 days or less past due | Credit Concentration Risk | Accounts receivable, net    
Concentration Risk [Line Items]    
Concentration risk, percentage 97.00% 95.00%
59 days or less past due | Credit Concentration Risk | Accounts receivable, net    
Concentration Risk [Line Items]    
Concentration risk, percentage 99.00% 97.00%