Stock-Based Compensation Plans - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands |
12 Months Ended | ||
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Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
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Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
Share-based compensation expense - Independent contractors | $ 4,870 | $ 3,314 | $ 4,159 |
Allocated share-based compensation expense | 9,145 | 7,035 | 7,114 |
Employee Stock Purchase Plan [Member] | |||
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
Allocated share-based compensation expense | 128 | 169 | 285 |
Restricted Stock Awards [Member] | Non-Employee Directors [Member] | |||
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
Allocated share-based compensation expense | 397 | 422 | 319 |
Restricted Stock Units [Member] | Employees [Member] | |||
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
Allocated share-based compensation expense | $ 3,750 | $ 3,130 | $ 2,351 |
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- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Fair value of share-based compensation granted to nonemployees as payment for services rendered or acknowledged claims. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
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