Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation - Additional Information (Details)

v3.20.4
Share-Based Compensation - Additional Information (Details)
$ / shares in Units, $ in Millions
12 Months Ended
Oct. 30, 2012
shares
Dec. 31, 2020
USD ($)
Installment
$ / shares
shares
Dec. 31, 2019
USD ($)
$ / shares
shares
Dec. 31, 2018
USD ($)
$ / shares
Modified Award [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Phantom shares vested | shares   600,719    
Restricted Stock [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Number of annual installments | Installment   3    
Weighted Average Grant Date Fair Value Per, Granted   $ 149.38 $ 96.59 $ 91.85
Weighted average grant date fair value per, vested | $   $ 11.9 $ 7.3 $ 6.2
Unrecognized stock-based compensation cost | $   $ 9.9    
Unrecognized compensation costs, weighted-average recognition periods   1 year 8 months 12 days    
Phantom shares vested | shares   80,349    
Unvested Weighted Average grant date fair value   $ 121.53 $ 90.65  
PBRSUs [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Weighted Average Grant Date Fair Value Per, Granted [1]   $ 146.29    
Unrecognized stock-based compensation cost | $   $ 1.9    
Unrecognized compensation costs, weighted-average recognition periods   2 years 1 month 6 days    
Unvested Weighted Average grant date fair value   $ 146.29    
Phantom Stock Plan [Member] | Modified Award [Member] | ASU 2017-09 [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Weighted Average Grant Date Fair Value Per, Granted     $ 120.41  
Share based compensation outstanding number | shares     613,996  
Vested Phantom Stock Plan [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Weighted Average Grant Date Fair Value Per, Granted   120.56    
Phantom Share Units (PSUs)        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized | shares 1,500,000      
Share-based compensation arrangement vesting increment percentage 20.00%      
Share based compensation arrangement, employment period for eligibility of employees participation 10 years      
Unvested Weighted Average grant date fair value   $ 113.65    
Liability for unsettled stock awards | $   $ 0.0    
Stock Incentive Plan 2016 [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized | shares   3,000,000    
[1] Amount represents PBRSUs granted at target. PBRSUs earned may range from zero to 200% of the target award. Actual PBRSUs earned for the 2020 performance period, as determined by the Compensation Committee, were equal to the target amount.