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Stock-Based Compensation Plans and Employee Benefits - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Class Of Stock [Line Items]      
Share-based payments award, number of shares available for grant 3,700,000    
Black-Scholes Option Pricing Model [Member]      
Class Of Stock [Line Items]      
Share-based compensation arrangement by share-based payment award, shares granted 0 0  
Stock options [Member]      
Class Of Stock [Line Items]      
Contractual term of stock options, Maximum 10 years    
RSUs [Member]      
Class Of Stock [Line Items]      
Restricted common shares 300,000 300,000 400,000
Restricted Stock [Member]      
Class Of Stock [Line Items]      
Share-based compensation arrangement by share-based payment award, shares granted 260,000    
Weighted-average fair value of the restricted stock $ 13.59    
Common shares issued 100,000 100,000  
Total unrecognized compensation cost granted $ 12.0    
Term of recognition of unrecognized stock option compensation cost 1 year 6 months    
Restricted Stock [Member] | Minimum [Member]      
Class Of Stock [Line Items]      
Vesting period 3 years    
Weighted-average fair value of the restricted stock $ 11.64    
Restricted Stock [Member] | Maximum [Member]      
Class Of Stock [Line Items]      
Vesting period 4 years    
Weighted-average fair value of the restricted stock $ 30.31    
Performance-Based Restricted Share Units (PRSUs) [Member]      
Class Of Stock [Line Items]      
Share-based compensation arrangement by share-based payment award, shares granted 0 0  
Performance-based restricted share units, description In 2019 and 2018, the Board of Directors approved grants to the chief executive officer, chief operating officer and former chief financial officer of PRSUs covering a “target” number of shares, subject to performance periods beginning on March 1, 2019 and March 1, 2018, respectively, and ending on February 28, 2022 and February 28, 2021, respectively.  In 2017, the Board of Directors approved grants to the chief executive officer, chief operating officer and former chief financial officer of PRSUs covering a “target” number of shares, subject to one-year, two-year and three-year performance periods beginning on March 1, 2017.    
Performance-based restricted share units, fair value equity and liability awards $ 5.6 $ 4.7 $ 3.9
Share based compensation arrangement by share based payment award, mark to market adjustment $ 1.9    
Performance-Based Restricted Share Units (PRSUs) [Member] | Minimum [Member]      
Class Of Stock [Line Items]      
Share-based compensation arrangement by share-based payment award, target 0.00%    
Performance-Based Restricted Share Units (PRSUs) [Member] | Maximum [Member]      
Class Of Stock [Line Items]      
Share-based compensation arrangement by share-based payment award, target threshold 200.00%