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Stock-Based Compensation - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Restricted Stock Units (RSU) [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
The vesting graded scale The vesting of RSUs is generally based on the passage of time, generally over a three -year period or in certain instances the RSUs were issued with five-year cliff vesting.    
Performance Share Awards (PSAs) [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Cumulative performance targets 2 years    
Additional service period 1 year    
Grants under performance share awards 171,150 218,422 184,834
Weighted average grant date fair value $ 16.65 $ 15.86 $ 20.20
Restricted Stock Units (RSU) and Performance Share Awards (PSAs) [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Grants under performance share awards 400,854 600,820 435,542
Unrecognized compensation expense for outstanding RSUs and PSAs $ 5.4    
The weighted average remaining period over which the expense will be recognized 1 year 7 months 6 days    
Stock Only Stock Appreciation Rights (SOSARs) [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period of stock 3 years    
Share-based payment award, shares issued in period 0 0 0
Intrinsic value of SOSARs vested and expected to vest $ 0.1    
The remaining weighted average contractual life of outstanding SOSARs 3 years 6 months    
Long Term Incentive Plan [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Common stock available for future issuance 1,899,527