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Related-Party Transactions - Additional Information (Detail) - USD ($)
3 Months Ended 12 Months Ended
Nov. 05, 2017
Dec. 31, 2017
Dec. 31, 2017
Dec. 31, 2016
Dec. 01, 2009
Term B-2 Loans [Member]          
Related Party Transaction [Line Items]          
Debt instrument, balance         $ 1,405,000,000
ZHG Stock Purchase Agreement [Member]          
Related Party Transaction [Line Items]          
Revenue recognized     $ 3,900,000    
Reimbursement for cost and expenses incurred by company relating to sale     $ 4,000,000    
Hill Path Capital LP (“Hill Path”) [Member]          
Related Party Transaction [Line Items]          
Reimbursement for fees and expenses incurred in connection with the agreement   $ 500,000      
Related party transaction, Agreement entered date Nov. 05, 2017        
Agreement effective period, description     12 months following the date on which there is no director serving on the Board who is designated by Hill Path.    
Blackstone and Affiliates [Member] | Term B-2 Loans [Member]          
Related Party Transaction [Line Items]          
Debt instrument, balance   $ 0 $ 0 $ 25,000,000