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Stock Plans - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2019
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock options exercisable period after grant date   3 years    
Restricted stock and restricted stock unit vest period after grant date   3 years    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value     0 0
Average closing share price, period       1 year
Cash proceeds from exercise of options   $ 7,471 $ 8,573 $ 18,465
Aggregate intrinsic value of stock options exercisable   44,500    
Aggregate intrinsic value of stock options outstanding   45,100    
Total intrinsic value of stock options exercised   14,600 12,200 29,300
Unrecognized stock-based compensation expense   $ 11,600    
Weighted average period over which unrecognized stock-based compensation expense is expected to be recognized, in years   1 year 6 months 10 days    
Minimum        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Percentage of target award based on achieving targeted performance conditions   0.00%    
Maximum        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Percentage of target award based on achieving targeted performance conditions   200.00%    
Percentage of target award based on achieving targeted return on net assets based on which final number of shares to be issued for performance stock units   237.60%    
Stock Options        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Excess tax benefit (provision) related to stock plans   $ 4,800 2,500 7,400
Restricted Stock and Unit Activity        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Fair value of stock units vested   5,500 5,400 4,100
Performance Stock Unit Activity        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Award vesting period (in years) 3 years      
Fair value of stock units vested   $ 6,200 $ 1,700 $ 4,100
Management        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Shares reserved for future grants   903,802    
Non Employee Directors        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Shares reserved for future grants   103,098    
Stock Options        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock options expiration period   10 years