Stock-based Compensation - Unrecognized Compensation Costs for Stock Options, Stock Awards and SARs (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation costs for stock options, stock awards and SARs	$ 2,441	$ 1,850
Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation costs for stock options, stock awards and SARs	5,518	3,618
SARs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation costs for stock options, stock awards and SARs	$ 5,314	$ 4,058