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Stock-Based Compensation Plans (Details) $ / shares in Units, $ in Thousands | 12 Months Ended
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Dec. 31, 2016 USD ($) Plan $ / shares shares | Dec. 31, 2015 USD ($) $ / shares shares | Dec. 31, 2014 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Stock-based compensation expense | $ | $ 6,127 | $ 5,379 | $ 4,843
Restricted and performance-based stock, weighted average grant date fair value per share [Roll Forward] |  |  |
Weighted-average grant date fair value | $ | $ 25,100 | 20,600 | 18,400
Performance-Based Shares [Member] |  |  |
Restricted and Performance Stock Grants [Abstract] |  |  |
Measuring period for performance-based shares | 3 years |  |
Award vesting rights | Selected executives and other key personnel are granted performance awards whose vesting is contingent upon meeting various performance measures with a retention feature. Performance-based shares are subject to a three year measuring period and the achievement of performance targets and, depending upon the achievement of such performance targets, they may become vested on the third anniversary of the date of grant. |  |
Restricted Shares [Member] |  |  |
Restricted and Performance Stock Grants [Abstract] |  |  |
Award vesting rights | Restricted shares granted to employees become fully vested upon the third anniversary of the date of grant; and for selected key executives certain additional restricted share grants vest 25% upon the attainment of age 60, 25% upon the attainment of age 63 and become fully vested upon the attainment of age 65. Restricted shares granted to directors become fully vested upon the first anniversary of the date of grant. Commencing with the 2015 grants, restricted and performance shares issued to certain key executives and directors are subject to a one or two year holding period upon the lapse of the three year vesting period. |  |
Restricted Shares [Member] | Age 60 [Member] |  |  |
Restricted and Performance Stock Grants [Abstract] |  |  |
Vesting percentage | 25.00% |  |
Restricted Shares [Member] | Age 63 [Member] |  |  |
Restricted and Performance Stock Grants [Abstract] |  |  |
Vesting percentage | 25.00% |  |
Restricted Shares [Member] | Age 65 [Member] |  |  |
Restricted and Performance Stock Grants [Abstract] |  |  |
Vesting percentage | 100.00% |  |
Restricted and Performance-Based Shares [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Stock-based compensation expense | $ | $ 5,700 | 5,000 | 4,300
Stock-based compensation expense, net of tax | $ | 3,600 | 3,200 | $ 2,800
Unamortized compensation expense | $ | $ 15,600 | $ 12,700 |
Restricted and performance-based stock, shares [Roll Forward] |  |  |
Beginning of period (in shares) | 758,550 | 749,018 |
Granted (in shares) | 212,500 | 211,950 |
Vested (in shares) | (138,427) | (192,768) |
Forfeited (in shares) | (9,775) | (9,650) |
End of period (in shares) | 822,848 | 758,550 | 749,018
Restricted and performance-based stock, weighted average grant date fair value per share [Roll Forward] |  |  |
Beginning of period (in dollars per share) | $ / shares | $ 27.19 | $ 24.62 |
Granted (in dollars per share) | $ / shares | 42.93 | 31.79 |
Vested (in dollars per share) | $ / shares | 31.55 | 22.13 |
Forfeited (in dollars per share) | $ / shares | 31.79 | 29.30 |
End of period (in dollars per share) | $ / shares | $ 30.46 | $ 27.19 | $ 24.62
Restricted and Performance-Based Shares [Member] | Employees [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Weighted average period of recognition for unrecognized compensation expense | 5 years 8 months 12 days | 5 years 9 months 18 days |
Restricted and Performance Stock Grants [Abstract] |  |  |
Estimated forfeitures | 5.00% |  |
Restricted and Performance-Based Shares [Member] | Executives [Member] |  |  |
Restricted and Performance Stock Grants [Abstract] |  |  |
Estimated forfeitures | 0.00% |  |
Restricted and Performance-Based Shares [Member] | Directors [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Weighted average period of recognition for unrecognized compensation expense | 3 months 18 days | 3 months 18 days |
Restricted and Performance Stock Grants [Abstract] |  |  |
Estimated forfeitures | 0.00% |  |
Restricted and Performance-Based Shares [Member] | Executives and Directors [Member] |  |  |
Restricted and Performance Stock Grants [Abstract] |  |  |
Expiration of vesting period | 3 years |  |
Restricted and Performance-Based Shares [Member] | Executives and Directors [Member] | Minimum [Member] |  |  |
Restricted and Performance Stock Grants [Abstract] |  |  |
Holding period for restricted and performance shares issued | 1 year |  |
Post vesting holding period for restricted and performance shares issued | 1 year |  |
Restricted and Performance-Based Shares [Member] | Executives and Directors [Member] | Maximum [Member] |  |  |
Restricted and Performance Stock Grants [Abstract] |  |  |
Holding period for restricted and performance shares issued | 2 years |  |
Post vesting holding period for restricted and performance shares issued | 2 years |  |
2006 Omnibus Incentive Plan [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Share-based compensation basic and diluted (in dollars per share) | $ / shares |  | $ 0.14 | $ 0.12
2016 Omnibus Incentive Plan [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Number of stock-based compensation plans | Plan | 1 |  |
Shares authorized for issuance (in shares) | 1,100,000 |  |
Share-based compensation basic and diluted (in dollars per share) | $ / shares | $ 0.16 |  |
2016 Omnibus Incentive Plan [Member] | Performance-Based Shares [Member] |  |  |
Restricted and performance-based stock, shares [Roll Forward] |  |  |
Granted (in shares) | 49,500 |  |
2016 Omnibus Incentive Plan [Member] | Restricted Shares [Member] |  |  |
Restricted and performance-based stock, shares [Roll Forward] |  |  |
Granted (in shares) | 163,000 |  |
2016 Omnibus Incentive Plan [Member] | Restricted and Performance-Based Shares [Member] |  |  |
Restricted and Performance Stock Grants [Abstract] |  |  |
Restricted and performance-based stock grants issued, net of forfeitures (in shares) | 212,500 |  |
Common stock available for future grants (in shares) | 887,500 |  |

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- Definition The 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 No definition available. + Details
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- Definition Post vesting holding period that once the award vests the participant needs to hold the award for a given time period until they can exercise the award. + References No definition available. + Details
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- Definition Represents the measuring period for performance-based shares. + References No definition available. + Details
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- Definition Post vesting holding period that once the award vests the participant needs to hold the award for a given time period until they can exercise the award. + References No definition available. + Details
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- Definition Element represents the amount of share based compensation for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period. + References No definition available. + Details
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- Definition The amount of expense, net of income tax, 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 No definition available. + Details
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- Definition Aggregate number of common shares reserved for future issuance. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + 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://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=6415400&loc=d3e5070-113901 + Details
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- Definition The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585 + Details
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- Definition Description of award terms as to how many shares or portion of an award are no longer contingent on satisfaction of either a service condition, market condition or a performance condition, thereby giving the employee the legal right to convert the award to shares, to sell the shares, and be entitled to the cash proceeds of such sale. For example, vesting may be expressed as being 25 percent of the shares under option on each anniversary of the grant 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 (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&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://www.xbrl.org/2003/role/presentationRef -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=6415400&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://www.xbrl.org/2003/role/presentationRef -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=6415400&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=6415400&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=6415400&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://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=6415400&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://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=6415400&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://www.xbrl.org/2003/role/presentationRef -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=6415400&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://www.xbrl.org/2003/role/presentationRef -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=6415400&loc=d3e5070-113901 + Details
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- Definition The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested). + 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 (a)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Percentage of vesting 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 (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Period from grant date that an equity-based award expires, 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 (a)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Number of shares issued during the period related to Restricted Stock Awards, net of any shares forfeited. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(28)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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