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Stock-Based Compensation - Schedule of Information Related to Outstanding SOSARS (Detail) - USD ($) $ / shares in Units, $ in Thousands | 12 Months Ended
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Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Exercised | (22,000) | (26,000) | (110,000)
Stock Only Stock Appreciation Rights (SOSARs) [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Beginning Balance, Outstanding | 2,199,742 | 1,864,707 | 1,977,133
Granted | 743,925 | 423,590 | 281,881
Exercised | (61,190) | (70,347) | (364,465)
Canceled / forfeited | (145,861) | (18,208) | (29,842)
Ending Balance, Outstanding | 2,736,616 | 2,199,742 | 1,864,707
Exercisable at December 31 | 1,740,591 | 1,504,599 | 1,285,998
Vested and expected to vest | 2,725,611 | 2,178,708 | 1,754,295
Beginning Balance, Weighted Average Exercise Price, Outstanding | $ 17.82 | $ 16.20 | $ 13.91
Weighted Average Exercise Price, Granted | 17.54 | 24.62 | 29.78
Weighted Average Exercise Price, Exercised | 10.70 | 14.12 | 13.99
Weighted Average Exercise Price, Canceled / forfeited | 22.80 | 25.41 | 19.36
Ending Balance, Weighted Average Exercise Price, Outstanding | 17.64 | 17.82 | 16.20
Weighted Average Exercise Price, Exercisable at December 31, | 16.19 | 14.48 | 12.94
Weighted average grant date fair value per share | $ 4.07 | $ 7.46 | $ 9.81
Aggregate grant date fair value | $ 3,013 | $ 3,134 | $ 2,764
Black-Scholes assumptions |  |  |
Dividend yield | 2.85% | 1.94% | 1.48%
Risk free rate of return | 1.34% | 1.64% | 1.74%
Volatility | 31.97% | 36.38% | 37.59%
Expected life | 6 years | 6 years | 6 years
Compensation expense | $ 2,735 | $ 2,645 | $ 2,086

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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://www.xbrl.org/2003/role/presentationRef -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=27013229&loc=d3e301413-122809 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -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=6415400&loc=d3e5070-113901 + Details
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- Definition The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. + 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 (f)(2)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The risk-free interest rate assumption that is used in valuing an option on its own shares. + 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 (f)(2)(iv) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average expected volatility rate of share-based compensation awards. + 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 (f)(2)(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan. + 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)(1)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Expected term of share-based compensation awards, 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 (f)(2)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.D.2) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 + Details
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