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Equity Plans Restricted Stock and Deferred Restricted Stock Activity (Details) - USD ($) $ / shares in Units, $ in Thousands |  |  |  | 12 Months Ended
--- | --- | --- | --- | ---
Apr. 25, 2018 | Jan. 30, 2018 | Apr. 26, 2017 | Dec. 31, 2018
Restricted Stock and Deferred Restricted Stock [Member] |  |  |  |
Restricted and Deferred Restricted Stock Awards Outstanding [Roll Forward] |  |  |  |
Outstanding as of January 1, 2016, units |  |  |  | 190,496
Issued, units |  |  |  | 58,211
Exercised, units |  |  |  | (143,614)
Forfeited or expired |  |  |  | 0
Outstanding as of December 31, 2016, units |  |  |  | 105,093
Shares vested as of December 31, 2016, shares |  |  |  | 45,912
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Weighted Average Grant Date Fair Value [Roll Forward] [Roll Forward] |  |  |  |
Outstanding as of January 1, 2016, wtd avg grant date fair value |  |  |  | $ 27.81
Issued, wtd avg grant date fair value |  |  |  | 50.29
Exercised, wtd avg grant date fair value |  |  |  | 28.41
Forfeited or expired, wtd avg grant date fair value |  |  |  | 0.00
Outstanding as od December 31, 2016, wtd avg grant date fair value |  |  |  | 37.73
Shares vested as of December 31, 2016, wtd avg grant date fair value |  |  |  | $ 16.46
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] |  |  |  |
Nonvested as of January 1, 2016, units |  |  |  | 87,483
Granted, units |  |  |  | 58,211
Vested, units |  |  |  | (86,513)
Forfeited, units |  |  |  | 0
Nonvested as of December 31, 2016, units |  |  |  | 59,181
Restricted and Deferred Restricted Stock Awards, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward] |  |  |  |
Nonvested as of January 1, 2016, wtd avg grant date fair value |  |  |  | $ 40.89
Granted, wtd avg grant date fair value |  |  |  | 50.29
Vested, wtd avg grant date fair value |  |  |  | 35.99
Forfeited, wtd avg grant date fair value |  |  |  | 0.00
Nonvested as of December 31, 2016, wtd avg grant date fair value |  |  |  | $ 54.67
Unrecognized compensation cost |  |  |  | $ 1,801
Period for recognition of compensation cost |  |  |  | 1 year 2 months 12 days
Officer [Member] | Performance Shares [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] |  |  |  |
Granted, units |  | 4,081 |  |
Restricted and Deferred Restricted Stock Awards, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Percentage Of Target Number Of Shares Expected To Vest |  |  |  | 150.00%
Officer [Member] | Performance Shares 2 [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] |  |  |  |
Granted, units |  | 5,259 |  |
Restricted and Deferred Restricted Stock Awards, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward] |  |  |  |
Granted, wtd avg grant date fair value |  | $ 55.89 |  |
Officer [Member] | Performance Shares 3 [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] |  |  |  |
Granted, units |  | 6,342 |  |
Restricted and Deferred Restricted Stock Awards, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward] |  |  |  |
Granted, wtd avg grant date fair value |  | $ 63.85 |  |
Officer [Member] | Minimum [Member] | Performance Shares [Member] |  |  |  |
Restricted and Deferred Restricted Stock Awards, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage |  | 0.00% |  |
Officer [Member] | Minimum [Member] | Performance Shares 2 [Member] |  |  |  |
Restricted and Deferred Restricted Stock Awards, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Percentage Of Target Number Of Shares Expected To Vest |  |  |  | 50.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage |  | 0.00% |  |
Officer [Member] | Minimum [Member] | Performance Shares 3 [Member] |  |  |  |
Restricted and Deferred Restricted Stock Awards, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage |  | 0.00% |  |
Officer [Member] | Maximum [Member] | Performance Shares [Member] |  |  |  |
Restricted and Deferred Restricted Stock Awards, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward] |  |  |  |
Granted, wtd avg grant date fair value |  | $ 58.02 |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage |  | 150.00% |  |
Officer [Member] | Maximum [Member] | Performance Shares 2 [Member] |  |  |  |
Restricted and Deferred Restricted Stock Awards, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Percentage Of Target Number Of Shares Expected To Vest |  |  |  | 100.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage |  | 150.00% |  |
Officer [Member] | Maximum [Member] | Performance Shares 3 [Member] |  |  |  |
Restricted and Deferred Restricted Stock Awards, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage |  | 200.00% |  |
Non-employee Board Members [Member] | Restricted Stock Units (RSUs) [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] |  |  |  |
Granted, units |  |  | 7,385 |
Restricted and Deferred Restricted Stock Awards, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward] |  |  |  |
Granted, wtd avg grant date fair value | $ 55.8 |  |  |

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- Definition Unrecognized cost of unvested share-based compensation awards. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(3) -URI http://asc.fasb.org/extlink&oid=109197908&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://fasb.org/us-gaap/role/ref/legacyRef -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=109197908&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://fasb.org/us-gaap/role/ref/legacyRef -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=109197908&loc=d3e5070-113901 + 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://fasb.org/us-gaap/role/ref/legacyRef -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=109197908&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -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=109197908&loc=d3e5070-113901 + Details
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- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(2) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(2) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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