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Sale of Accounts Receivable - Additional Information (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Restricted cash   $ 3,300,000
Receivables purchase agreement    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Receivables purchase agreement - description of arrangements The term of the agreement is for 364 days and shall automatically be extended for annual successive terms unless terminated. Either party may terminate the agreement at any time upon sixty days' prior written notice to the other party.  
Agreement period 364 days  
Agreement period, extension term   Automatically be extended for annual successive terms unless terminated
Agreement termination, written notice period 60 days  
Sale of receivables $ 90,200,000 $ 44,300,000
Receivables purchase agreement | Selling, general and administrative expenses    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Charge related to sale of receivables $ 328,000,000 131,000,000
Receivables purchase agreement | Maximum    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Receivables purchase agreement - maximum borrowing   $ 25,000,000