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Stock-based Compensation - Unrecognized Compensation Costs for Stock Options, Stock Awards and SARs (Detail) - USD ($)
$ in Thousands
Sep. 30, 2021
Dec. 31, 2020
Stock Option [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Unrecognized compensation costs for stock options, stock awards and SARs $ 2,739 $ 1,993
Stock Awards [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Unrecognized compensation costs for stock options, stock awards and SARs 6,728 5,313
SARs [Member]    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Unrecognized compensation costs for stock options, stock awards and SARs $ 5,931 $ 4,341