Stock-based Compensation - Unrecognized Compensation Costs for Stock Options, Stock Awards and SARs (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation costs for stock options, stock awards and SARs	$ 2,557	$ 1,655
Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation costs for stock options, stock awards and SARs	4,959	3,180
SARs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation costs for stock options, stock awards and SARs	$ 5,473	$ 3,566