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Deferred Compensation Agreements and Stock-Based Compensation - Restricted Stock Units (Details) - USD ($) $ / shares in Units, $ in Thousands | 12 Months Ended | 56 Months Ended
--- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2017
Weighted Average Grant Date Fair Value per Unit |  |  |  |
Accrued dividend equivalent units | 3,097 |  |  | 3,097
Restricted Stock Units |  |  |  |
Units |  |  |  |
Granted, Units |  |  |  | 259,065
Weighted Average Grant Date Fair Value per Unit |  |  |  |
Number of Units to Vest | 85,415 |  |  | 85,415
Restricted Stock Units | 2018 |  |  |  |
Weighted Average Grant Date Fair Value per Unit |  |  |  |
Number of Units to Vest | 28,471 |  |  | 28,471
Restricted Stock Units | 2019 |  |  |  |
Weighted Average Grant Date Fair Value per Unit |  |  |  |
Number of Units to Vest | 51,552 |  |  | 51,552
Restricted Stock Units | 2020 |  |  |  |
Weighted Average Grant Date Fair Value per Unit |  |  |  |
Number of Units to Vest | 5,392 |  |  | 5,392
Equity Plan | Restricted Stock Units |  |  |  |
Units |  |  |  |
Beginning Balance, Units | 149,809 |  |  |
Granted, Units | 10,000 | 100,553 | 0 | 259,065
Vested, Units | (74,394) |  |  |
Ending Balance, Units | 85,415 | 149,809 |  | 85,415
Weighted Average Grant Date Fair Value per Unit |  |  |  |
Beginning Balance, Weighted Average Grant Date Fair Value per Unit | $ 24.70 |  |  |
Granted, Weighted Average Grant Date Fair Value per Unit | 22.90 | $ 23.87 |  |
Vested, Weighted Average Grant Date Fair Value per Unit | 25.53 |  |  |
Ending Balance, Weighted Average Grant Date Fair Value per Unit | $ 23.76 | $ 24.70 |  | $ 23.76
Total fair value of Units vested | $ 1,700 | $ 600 | $ 900 |
Number of vested units | 173,650 |  |  | 173,650
Compensation expense recognized | $ 1,100 | $ 1,600 | $ 1,100 |
Unrecognized compensation expense | $ 1,200 |  |  | $ 1,200
Period to recognize unrecognized compensation expense | 1 year 7 months 6 days |  |  |
Accrued dividend equivalent units | 3,097 |  |  | 3,097
Executives | Equity Plan | Restricted Stock Units |  |  |  |
Units |  |  |  |
Granted, Units |  |  |  | 259,065

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- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that are scheduled to vest. + References No definition available. + Details
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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=96867065&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=96867065&loc=d3e5070-113901 + Details
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- Definition Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation. + 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 (i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target 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)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target 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)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash. + 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 (d)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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