v3.6.0.2
Share-based Compensation - Summary of Performance Share Units (Detail) - Long Term Incentive Plans [Member] - Performance Share Units [Member] - $ / shares
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Financial Performance Conditions [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares, Outstanding at January 1, 2016 775,324    
Shares, Granted 32,716    
Shares, Vested 398,951    
Shares, Forfeited 375    
Shares, Outstanding at December 31, 2016 408,714 775,324  
Weighted average grant date fair value, Outstanding at January 1, 2016 $ 49.68    
Weighted average grant date fair value, Granted 82.53 $ 75.28 $ 62.29
Weighted average grant date fair value, Vested 30.00    
Weighted average grant date fair value, Forfeited 49.60    
Weighted average grant date fair value, Outstanding at December 31, 2016 $ 71.52 $ 49.68  
Market Performance Conditions [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares, Outstanding at January 1, 2016 1,905,269    
Shares, Vested 1,580,086    
Shares, Outstanding at December 31, 2016 325,183 1,905,269  
Weighted average grant date fair value, Outstanding at January 1, 2016 $ 26.85    
Weighted average grant date fair value, Vested 27.28    
Weighted average grant date fair value, Outstanding at December 31, 2016 $ 38.63 $ 26.85