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Stock-Based Compensation - Summary of Stock-Based Compensation Expenses (Detail) - USD ($) $ in Thousands | 3 Months Ended
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Mar. 31, 2019 | Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Stock-based compensation expense | $ 2,793 | $ 2,306
Stock Appreciation Rights [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Stock-based compensation expense | 295 | 202
Time-Based Restricted Stock and Restricted Stock Units [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Stock-based compensation expense | 1,149 | 822
Performance-Based Restricted Stock and Restricted Stock Units [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Stock-based compensation expense | 1,314 | 1,249
Employee Stock Purchase Plan [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Stock-based compensation expense | $ 35 | $ 33

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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. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5047-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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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. + References No definition available. + Details
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