Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation Plans - Stock-Based Compensation Expense (Detail)

v3.20.4
Stock-Based Compensation Plans - Stock-Based Compensation Expense (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Allocated share-based compensation expense $ 9,905 $ 9,278 $ 11,983
Employee Stock Purchase Plan [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Allocated share-based compensation expense 168 139 109
Restricted Stock Awards [Member] | Non-Employee Directors [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Allocated share-based compensation expense 606 643 632
Restricted Stock Units [Member] | Employees [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Allocated share-based compensation expense 6,003 5,419 4,233
Restricted Stock Units [Member] | Independent Contractors, Subsequent to Adoption of New Standard [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Allocated share-based compensation expense $ 3,128 $ 3,077  
Restricted Stock Units [Member] | Independent Contractors, Prior to Adoption of New Standard [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation expense - Independent contractors     $ 7,009