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Share-based Compensation - Schedule of Changes in Time-Based, Performance-Based and Market-Based Restricted Stock Awards and Stock Units (Detail) - $ / shares
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Time-based Restricted Stock Awards and Stock Units [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Outstanding at December 31, 2017 325,874    
Granted (in shares) 172,108    
Vested and settled (in shares) (112,249)    
Cancelled (in shares) (28,141)    
Outstanding at December 31, 2018 357,592 325,874  
Outstanding at December 31, 2017 $ 42.44    
Granted (in dollars per share) 57.18    
Vested and settled (in dollars per share) 40.08    
Cancelled (in dollars per share) 48.84    
Outstanding at December 31, 2018 $ 49.77 $ 42.44  
Performance-based Restricted Stock Awards and Stock Units [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Outstanding at December 31, 2017 109,880    
Granted (in shares) 0 0 0
Cancelled (in shares) (7,725)    
Outstanding at December 31, 2018 102,155 109,880  
Outstanding at December 31, 2017 $ 33.12    
Cancelled (in dollars per share) 33.12    
Outstanding at December 31, 2018 $ 33.12 $ 33.12  
Market-based Restricted Stock Units [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Outstanding at December 31, 2017 187,314    
Granted (in shares) 97,420 94,902 96,245
Cancelled (in shares) (13,439)    
Outstanding at December 31, 2018 271,295 187,314  
Outstanding at December 31, 2017 $ 51.99    
Granted (in dollars per share) 68.38    
Cancelled (in dollars per share) 60.83    
Outstanding at December 31, 2018 $ 57.44 $ 51.99