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Stock-Based Compensation - Summary of Activity for Outstanding and Exercisable SARs (Detail) - Stock Appreciation Rights (SARs) [Member] - USD ($) | 12 Months Ended |
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Dec. 31, 2017 | Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Stock appreciation rights outstanding | 282,907 | 599,334
Stock appreciation rights exercisable | 221,375 |
Weighted Average Base Value, Stock appreciation rights outstanding | $ 28.62 |
Weighted Average Base Value, Stock appreciation rights exercisable | $ 27.92 |
Weighted Average Remaining Contractual Life, Stock appreciation rights outstanding | 3 years 3 months 19 days |
Weighted Average Remaining Contractual Life, Stock appreciation rights exercisable | 3 years |
Aggregate Intrinsic Value, Stock appreciation rights outstanding | $ 18,639 |
Aggregate Intrinsic Value, Stock appreciation rights exercisable | $ 14,740 |

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- Definition Share based compensation arrangement by share based payment award equity instruments other than options exercisable aggregate intrinsic value. + References No definition available. + Details
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- Definition Share based compensation arrangement by share based payment award equity instruments other than options exercisable weighted average base value. + References No definition available. + Details
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- Definition Share based compensation arrangement by share based payment award equity instruments other than options exercisable weighted average remaining contractual terms. + References No definition available. + Details
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- Definition Share based compensation arrangement by share based payment award equity instruments other than options outstanding weighted average base value. + References No definition available. + Details
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- Definition The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e)(1) -URI http://asc.fasb.org/extlink&oid=96867065&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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- Definition Intrinsic value of equity-based compensation awards outstanding. Excludes stock and unit options. + References No definition available. + Details
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- Details
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