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Significant Accounting Policies - Additional Information (Detail)
$ in Thousands
12 Months Ended
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Dec. 31, 2018
USD ($)
Mar. 31, 2018
USD ($)
Dec. 31, 2017
EUR (€)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
EUR (€)
Dec. 31, 2016
USD ($)
Sep. 30, 2016
Jun. 30, 2015
EUR (€)
Significant Accounting Policies [Line Items]                      
Loyalty program liability             $ 562,000   $ 442,000    
Advertising expense $ 3,300,000 $ 2,700,000 $ 2,100,000                
Prepaid marketing expenses             $ 38,000   23,000    
Effect of adoption                 $ (3,011)    
2.5% Senior Notes Due 2022                      
Significant Accounting Policies [Line Items]                      
Senior unsecured notes principal amount | €           € 650,000,000   € 650,000,000     € 650,000,000
Senior notes, interest rate           2.50% 2.50% 2.50% 2.50% 2.50% 2.50%
Stock Options                      
Significant Accounting Policies [Line Items]                      
Vesting period 4 years                    
Minimum                      
Significant Accounting Policies [Line Items]                      
Definite lived intangible assets, estimated useful life 1 year                    
Minimum | RSUs                      
Significant Accounting Policies [Line Items]                      
Vesting period 3 years                    
Maximum                      
Significant Accounting Policies [Line Items]                      
Definite lived intangible assets, estimated useful life 12 years                    
Maximum | RSUs                      
Significant Accounting Policies [Line Items]                      
Vesting period 4 years                    
Computer equipment | Minimum                      
Significant Accounting Policies [Line Items]                      
Property and equipment, estimated useful lives 3 years                    
Computer equipment | Maximum                      
Significant Accounting Policies [Line Items]                      
Property and equipment, estimated useful lives 5 years                    
Software Development | Minimum                      
Significant Accounting Policies [Line Items]                      
Property and equipment, estimated useful lives 3 years                    
Software Development | Maximum                      
Significant Accounting Policies [Line Items]                      
Property and equipment, estimated useful lives 5 years                    
Furniture and other equipment | Minimum                      
Significant Accounting Policies [Line Items]                      
Property and equipment, estimated useful lives 3 years                    
Furniture and other equipment | Maximum                      
Significant Accounting Policies [Line Items]                      
Property and equipment, estimated useful lives 5 years                    
Retained earnings                      
Significant Accounting Policies [Line Items]                      
Effect of adoption                 $ 7,037    
ASU 2016-09 | Early Adoption                      
Significant Accounting Policies [Line Items]                      
Excess tax benefits recognized $ (60,000) $ (40,000)                  
ASU 2016-09 | Early Adoption | Retained earnings                      
Significant Accounting Policies [Line Items]                      
Effect of adoption                 $ 7,037    
Forecast | ASU 2014-09 | Retained earnings | Minimum                      
Significant Accounting Policies [Line Items]                      
Effect of adoption         $ (15,000)            
Forecast | ASU 2014-09 | Retained earnings | Maximum                      
Significant Accounting Policies [Line Items]                      
Effect of adoption         (25,000)            
Forecast | ASU 2014-09 | Retained earnings | Loyalty Program | Minimum                      
Significant Accounting Policies [Line Items]                      
Effect of adoption         (45,000)            
Forecast | ASU 2014-09 | Retained earnings | Loyalty Program | Maximum                      
Significant Accounting Policies [Line Items]                      
Effect of adoption         (55,000)            
Forecast | ASU 2014-09 | Retained earnings | Variable Consideration | Minimum                      
Significant Accounting Policies [Line Items]                      
Effect of adoption         30,000            
Forecast | ASU 2014-09 | Retained earnings | Variable Consideration | Maximum                      
Significant Accounting Policies [Line Items]                      
Effect of adoption         $ 40,000            
Forecast | ASU 2016-16 | Retained earnings                      
Significant Accounting Policies [Line Items]                      
Effect of adoption       $ (25,000)