Annual report pursuant to Section 13 and 15(d)

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

v3.6.0.2
Stock-Based Compensation Plans - Stock-Based Compensation Expense (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation expense - Independent contractors $ 3,314 $ 4,159 $ 3,892
Allocated share-based compensation expense 7,035 7,114 5,034
Employee Stock Purchase Plan [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Allocated share-based compensation expense 169 285 128
Restricted Stock Awards [Member] | Non-Employee Directors [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Allocated share-based compensation expense 422 319 197
Restricted Stock Units [Member] | Employees [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Allocated share-based compensation expense $ 3,130 $ 2,351 $ 817