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Employee Share Plans - Additional Information (Detail) - USD ($)
12 Months Ended
May 09, 2019
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Holding period of stock   1 year    
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Method Used   Black-Scholes-Merton option-pricing model    
Fair value of stock options granted     $ 4.73 $ 3.49
Restricted Stock Awards [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Compensation cost for non-vested stock options weighted average period   1 year 7 days    
Unrecognized compensation cost for restricted stock awards   $ 10,300,000    
Total fair value of shares vested during period   3,900,000 $ 4,100,000 $ 3,400,000
Market value of shares awarded during period   $ 4,500,000 $ 5,100,000 $ 4,400,000
Performance Shares [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Options awarded under the plans vesting period   3 years    
Share-based compensation arrangement by share-based payment award, remaining contractual terms   3 years    
Achievement of an earnings per share target   70.00%    
Achievement of total growth in revenue   30.00%    
2019 Plan [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Share available for future grant 3,100,000      
Stock awards expiry 2029      
2014 Stock Incentive Plan [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Share available for future grant   2,200,000    
Employee Stock Purchase Plan [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Termination date of the Employee Stock Purchase Plan   Jun. 30, 2022    
Price an employee pays for shares as percentage of fair market value   85.00%    
Stock Option [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Percentage of incremental vesting schedule     25.00% 25.00%
Incremental vesting schedule period     4 years  
Stock options expiry date   6 years    
Options awarded under the plans vesting period   4 years    
Weighted-average grant-date fair value of stock options granted     $ 3,000,000.0 $ 2,300,000
Aggregate intrinsic value of stock options exercised   $ 18,800,000 $ 10,900,000 $ 9,400,000
Unrecognized compensation cost for non-vested stock option   $ 3,800,000    
Compensation cost for non-vested stock options weighted average period   1 year 10 days    
Maximum [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Shares purchased under ESPP   2,000,000    
Options awarded under the plans vesting period   4 years    
Maximum [Member] | Restricted Stock Awards [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Options awarded under the plans vesting period   4 years    
Restricted stock outstanding release from restriction period range   2022-05    
Maximum [Member] | Performance Shares [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Percentage of initial grant   200.00%    
Maximum [Member] | Employee Stock Purchase Plan [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
ESPP allows qualified employees to purchase shares of common stock   $ 25,000    
Minimum [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Options awarded under the plans vesting period   3 years    
Minimum [Member] | Restricted Stock Awards [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Options awarded under the plans vesting period   1 year    
Restricted stock outstanding release from restriction period range   2020-02