Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.2
Stock-Based Compensation Plans - Stock-Based Compensation Expense (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Allocated share-based compensation expense $ 2,585 $ 3,159 $ 4,926 $ 5,772
Employee Stock Purchase Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Allocated share-based compensation expense 38 24 68 63
Restricted Stock Awards [Member] | Non-Employee Directors [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Allocated share-based compensation expense 154 165 324 276
Restricted Stock Units [Member] | Employees [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Allocated share-based compensation expense 1,622 1,096 2,967 2,049
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 $ 771 $ 1,874 $ 1,567 $ 3,384