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Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Additional disclosures [Abstract] |  |  |
Stock-based compensation expense | $ 3,644 | $ 4,378 | $ 4,086
Restricted stock and restricted stock units, weighted average grant date fair value [Abstract] |  |  |
Number of shares available for future grant (in shares) | 2,813,597 |  |
Stock Options [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Stock awards vesting period | 4 years |  |
Stock awards termination period | 10 years |  |
Stock options [Roll Forward] |  |  |
Outstanding, beginning of period (in shares) | 230,174 |  |
Granted (in shares) | 1,500 |  |
Exercised (in shares) | (118,844) |  |
Expired (in shares) | (800) |  |
Outstanding, end of period (in shares) | 112,030 | 230,174 |
Exercisable, end of period (in shares) | 107,280 |  |
Expected to vest (in shares) | 4,750 |  |
Stock options, weighted average exercise price [Abstract] |  |  |
Outstanding, beginning of period (in dollars per share) | $ 24.35 |  |
Granted (in dollars per share) | 40.63 |  |
Exercised (in dollars per share) | 25.94 |  |
Expired (in dollars per share) | 24.46 |  |
Outstanding, end of period (in dollars per share) | 22.88 | $ 24.35 |
Exercisable, end of period (in dollars per share) | 22.41 |  |
Expected to vest (in dollars per share) | $ 33.52 |  |
Additional disclosures [Abstract] |  |  |
Weighted average remaining contractual term, outstanding, end of period | 2 years 1 month 17 days |  |
Weighted average remaining contractual term, exercisable, end of period | 1 year 10 months 2 days |  |
Weighted average remaining contractual term, expected to vest | 8 years 8 months 5 days |  |
Aggregate intrinsic value, outstanding, end of period | $ 15,656 |  |
Aggregate intrinsic value, exercisable, end of period | 1,544 |  |
Aggregate intrinsic value, expected to vest | 22 |  |
Stock-based compensation expense | 100 | $ 200 | 200
Proceeds from stock options exercised | 3,083 | 8,398 | 12,044
Tax benefits related to stock options exercised | 650 | 1,223 | 952
Intrinsic value of stock options exercised | 1,699 | 3,143 | 2,446
Fair value of shares vested during the year | 329 | 105 | 63
Restricted Stock [Member] |  |  |
Additional disclosures [Abstract] |  |  |
Stock-based compensation expense | $ 3,500 | $ 4,200 | 3,900
Restricted Stock [Member] | Employees [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Stock awards vesting period | 5 years |  |
Restricted Stock [Member] | Non-employee Directors [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Stock awards vesting period | 3 years |  |
Restricted Stock Units (RSUs) [Member] |  |  |
Restricted stock and restricted stock units [Roll Forward] |  |  |
Unvested, beginning of period (in shares) | 613,163 |  |
Forfeited (in shares) | (5,545) |  |
Vested (in shares) | (198,652) |  |
Granted (in shares) | 125,772 |  |
Unvested, end of period (in shares) | 534,738 | 613,163 |
Restricted stock and restricted stock units, weighted average grant date fair value [Abstract] |  |  |
Unvested, beginning of period (in dollars per share) | $ 22.62 |  |
Forfeited (in dollars per share) | 23.18 |  |
Vested (in dollars per share) | 22.34 |  |
Granted (in dollars per share) | 36.15 |  |
Unvested, end of period (in dollars per share) | $ 25.77 | $ 22.62 |
Restricted Stock Awards and Stock Units [Member] |  |  |
Additional disclosures [Abstract] |  |  |
Tax benefit on restricted stock awards | $ 2,500 | $ 2,900 | $ 1,500
Unrecognized compensation cost | $ 4,800 |  |
Unrecognized compensation cost, weighted average period of recognition | 2 years 1 month 6 days |  |

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- Definition The total fair value of equity-based awards 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 No definition available. + Details
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- Definition The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the 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 (h)(1)(i) -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 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 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=96867065&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=96867065&loc=d3e5070-113901 + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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