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Stock-Based Compensation Plans and Employee Benefits - Additional Information (Detail) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Class Of Stock [Line Items]      
Share-based payments award, number of shares available for grant 5.8    
2016 VSEP [Member]      
Class Of Stock [Line Items]      
Vesting period 7 years    
Compensation fully earned and vested description Awards under the 2016 VSEP, if earned, may result in the granting of common shares of the Company and time-vested RSUs to participants on future measurement dates based on a performance period beginning on February 9, 2016 and ending on December 31, 2018 (the “Performance Period”). As a result, in general, the total compensation available to participants under the 2016 VSEP, if any, will be fully earned only after approximately seven years (the Performance Period and the final four-year, time-based vesting period for RSUs).    
Settlement percentage of common shares 20.00%    
Settlement percentage of restricted stock units 80.00%    
Expected lapse percentage 20.00%    
Minimum [Member] | 2016 VSEP [Member]      
Class Of Stock [Line Items]      
Share price for vesting $ 17.41    
Maximum [Member] | 2016 VSEP [Member]      
Class Of Stock [Line Items]      
Share price for vesting $ 25.35    
Stock options [Member]      
Class Of Stock [Line Items]      
Contractual term of stock options, Maximum 10 years    
Vesting period 3 years    
Portion of increments granted for stock options one-third    
Term of increment grant one year after the date of grant.    
Total unrecognized compensation cost granted $ 0.8    
Term of recognition of unrecognized stock option compensation cost 1 year 7 months 6 days    
RSUs [Member]      
Class Of Stock [Line Items]      
Restricted common shares 0.5    
Restricted Stock [Member]      
Class Of Stock [Line Items]      
Vesting period 4 years    
Total unrecognized compensation cost granted $ 10.9    
Term of recognition of unrecognized stock option compensation cost 2 years 6 months    
Restricted common shares   0.2 0.3
Weighted-average fair value of the restricted stock $ 16.31    
Common shares issued 0.1 0.1 0.1
Restricted Stock [Member] | Minimum [Member]      
Class Of Stock [Line Items]      
Weighted-average fair value of the restricted stock $ 12.17    
Restricted Stock [Member] | Maximum [Member]      
Class Of Stock [Line Items]      
Weighted-average fair value of the restricted stock $ 19.26    
Time-based Vesting [Member] | 2016 VSEP [Member]      
Class Of Stock [Line Items]      
Vesting period 4 years    
Performance Awards [Member] | 2016 VSEP [Member]      
Class Of Stock [Line Items]      
Aggregate percentage of performance awards 1.4909%