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Share-Based Compensation (Details) $ / shares in Units, $ in Thousands | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Dec. 31, 2017 USD ($) $ / shares shares | Dec. 31, 2018 USD ($) $ / shares shares | Dec. 31, 2017 USD ($) $ / shares shares | Dec. 31, 2016 USD ($) $ / shares shares | Apr. 26, 2017 shares | Apr. 24, 2013 shares
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |
Number of plans |  | 4 |  |  |  |
Share-based compensation expense | $ |  | $ 8,314 | $ 5,891 | $ 3,875 |  |
Excess Tax Benefit from Share-based Compensation, before ASU adoption | $ |  | 2,060 | 1,168 |  |  |
Excess Tax Benefit on Stock Plans | $ |  | $ 0 | $ 0 | $ 686 |  |
Number of stock appreciation rights granted (in shares) |  |  | 0 | 0 |  |
Valuation assumptions |  |  |  |  |  |
Expected volatility, minimum |  | 25.00% | 25.00% | 29.00% |  |
Expected volatiity, maximum |  | 25.00% | 26.00% | 32.00% |  |
Weighted-average expected volatility |  | 25.00% | 26.00% | 32.00% |  |
Expected dividend yield, minimum |  | 1.20% | 1.20% | 1.30% |  |
Expected dividend yield, maximum |  | 1.20% | 1.30% | 1.50% |  |
Weighted-average expected dividend yield |  | 1.20% | 1.30% | 1.30% |  |
Expected term, in years |  | 5 years | 5 years | 5 years |  |
Risk-free interest rate, minimum |  | 2.60% | 1.70% | 1.10% |  |
Risk-free interest rate, maximum |  | 2.90% | 2.00% | 1.40% |  |
2010 Plan |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |
Shares authorized for future awards (in shares) |  |  |  |  |  | 1,500,000
Amended 2010 Plan |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |
Shares authorized for future awards (in shares) |  |  |  |  |  | 2,600,000
2017 Plan |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |
Shares authorized for future awards (in shares) |  |  |  |  | 1,200,000 |
Shares reserved for issuance (in shares) |  | 761,382 |  |  |  |
All Plans Excluding 2010 Plan |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |
Shares reserved for issuance (in shares) |  | 897,315 |  |  |  |
Stock Options |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |
Ratio of new awards that vest each year |  | one-third |  |  |  |
Vesting period of new awards granted (in years) |  | 3 years |  |  |  |
Contractual term of new awards (in years) |  | 10 years |  |  |  |
Weighted-average grant date fair value (in dollars per share) | $ / shares | $ 16.39 | $ 16.07 |  | $ 13.61 |  |
Total intrinsic value of stock options exercised | $ |  | $ 10,305 | $ 4,450 | $ 3,408 |  |
Aggregate intrinsic value of options outstanding | $ |  | $ 5,987 |  |  |  |
Weighted-average remaining contractual life for options outstanding (in years) |  | 5 years 11 months |  |  |  |
Weighted-average remaining contractual life for options exercisable (in years) |  | 4 years 6 months |  |  |  |
Unrecognized compensation cost for nonvested options | $ |  | $ 1,944 |  |  |  |
Compensation cost not yet recognized, weighted-average period for recognition (in years) |  | 1 year 4 months |  |  |  |
Shares activity |  |  |  |  |  |
Outstanding at beginning of year (in shares) |  | 1,135,608 |  |  |  |
Granted (in shares) |  | 202,623 |  |  |  |
Exercised (in shares) |  | (223,352) |  |  |  |
Forfeited (in shares) |  | (30,312) |  |  |  |
Outstanding at end of year (in shares) | 1,135,608 | 1,084,567 | 1,135,608 |  |  |
Exercisable at end of year (in shares) |  | 711,499 |  |  |  |
Weighted-Average Exercise Price |  |  |  |  |  |
Outstanding at beginning of year (in dollars per share) | $ / shares |  | $ 47.47 |  |  |  |
Granted (in dollars per share) | $ / shares |  | 67.85 |  |  |  |
Exercised (in dollars per share) | $ / shares |  | 26.33 |  |  |  |
Forfeited (in dollars per share) | $ / shares |  | 66.06 |  |  |  |
Outstanding at end of year (in dollars per share) | $ / shares | $ 47.47 | 55.11 | $ 47.47 |  |  |
Exercisable at end of year (in dollars per share) | $ / shares |  | $ 48.94 |  |  |  |
Restricted Share Awards |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |
Vesting period of new awards granted (in years) |  | 3 years |  |  |  |
Unrecognized compensation cost for nonvested options | $ |  | $ 1,196 |  |  |  |
Compensation cost not yet recognized, weighted-average period for recognition (in years) |  | 1 year 7 months |  |  |  |
Fair value of shares vested | $ |  | $ 978 | $ 1,463 | 1,970 |  |
Shares activity |  |  |  |  |  |
Nonvested at beginning of year (in shares) |  | 99,789 |  |  |  |
Granted (in shares) |  | 16,377 |  |  |  |
Vested (in shares) |  | (14,384) |  |  |  |
Forfeited (in shares) |  | (1,561) |  |  |  |
Nonvested at end of year (in shares) | 99,789 | 100,221 | 99,789 |  |  |
Weighted-Average Exercise Price |  |  |  |  |  |
Nonvested at beginning of year (in dollars per share) | $ / shares |  | $ 53.11 |  |  |  |
Granted (in dollars per share) | $ / shares |  | 67.70 |  |  |  |
Vested (in dollars per share) | $ / shares |  | 68.00 |  |  |  |
Forfeited (in dollars per share) | $ / shares |  | 67.39 |  |  |  |
Nonvested at end of year (in dollars per share) | $ / shares | $ 53.11 | $ 53.52 | $ 53.11 |  |  |
Performance Share Awards |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |
Vesting period of new awards granted (in years) |  | 3 years |  |  |  |
Unrecognized compensation cost for nonvested options | $ |  | $ 3,287 |  |  |  |
Compensation cost not yet recognized, weighted-average period for recognition (in years) |  | 1 year 10 months |  |  |  |
Fair value of shares vested | $ |  | $ 0 | $ 1,240 | 1,703 |  |
Maximum increase in the number of shares of common stock a participant receives based on the achievement of performance goals (as a percent) |  | 200.00% |  |  |  |
Lowest potential number of shares of common stock that could be received based on the achievement level of performance goals (in shares) |  | 0 |  |  |  |
Shares activity |  |  |  |  |  |
Nonvested at beginning of year (in shares) |  | 123,024 |  |  |  |
Granted (in shares) |  | 47,997 |  |  |  |
Forfeited (in shares) |  | (43,974) |  |  |  |
Nonvested at end of year (in shares) | 123,024 | 127,047 | 123,024 |  |  |
Weighted-Average Exercise Price |  |  |  |  |  |
Nonvested at beginning of year (in dollars per share) | $ / shares |  | $ 63.09 |  |  |  |
Granted (in dollars per share) | $ / shares |  | 67.84 |  |  |  |
Forfeited (in dollars per share) | $ / shares |  | 66.23 |  |  |  |
Nonvested at end of year (in dollars per share) | $ / shares | $ 63.09 | $ 63.80 | $ 63.09 |  |  |
Restricted Stock Units |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |
Vesting period of new awards granted (in years) |  | 3 years |  |  |  |
Unrecognized compensation cost for nonvested options | $ |  | $ 4,473 |  |  |  |
Compensation cost not yet recognized, weighted-average period for recognition (in years) |  | 2 years |  |  |  |
Fair value of shares vested | $ |  | $ 899 | $ 962 |  |  |
Shares activity |  |  |  |  |  |
Nonvested at beginning of year (in shares) |  | 43,125 |  |  |  |
Granted (in shares) |  | 83,380 |  |  |  |
Vested (in shares) |  | (15,427) |  |  |  |
Forfeited (in shares) |  | (9,123) |  |  |  |
Nonvested at end of year (in shares) | 43,125 | 101,955 | 43,125 |  |  |
Weighted-Average Exercise Price |  |  |  |  |  |
Nonvested at beginning of year (in dollars per share) | $ / shares |  | $ 64.67 |  |  |  |
Granted (in dollars per share) | $ / shares |  | 66.83 |  |  |  |
Vested (in dollars per share) | $ / shares |  | 58.27 |  |  |  |
Forfeited (in dollars per share) | $ / shares |  | 66.60 |  |  |  |
Nonvested at end of year (in dollars per share) | $ / shares | $ 64.67 | $ 67.23 | $ 64.67 |  |  |
Share-Based Liabilities |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |
Total share-based liabilities | $ | $ 175 | $ 213 | $ 175 |  |  |
Amounts paid out related to share-based liability awards | $ |  | $ 32 | $ 45 | $ 62 |  |

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- Definition Amount of cash paid related to share-based compensation liabilities. + 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 (d)(2) -URI http://asc.fasb.org/extlink&oid=109197908&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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The estimated measure of the maximum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period. + References No definition available. + Details
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- Definition The estimated measure of the minimum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period. + References No definition available. + Details
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- Definition The maximum risk-free interest rate assumption that is used in valuing an option on its own shares. + References No definition available. + Details
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- Definition The minimum risk-free interest rate assumption that is used in valuing an option on its own shares. + References No definition available. + Details
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- Definition Weighted average expected volatility rate of 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 (f)(2)(ii) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=109197908&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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109197908&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://fasb.org/us-gaap/role/ref/legacyRef -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=109197908&loc=d3e5070-113901 + Details
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- Definition The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option 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)(1)(iii) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + 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 (d)(2) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option 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)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Net number of share options (or share units) granted during the 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)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. + 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 (d)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding. + 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 -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Number of options outstanding, including both vested and non-vested options. + 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 -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 Reference 2: 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)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
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- Definition Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option 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)(1)(i) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Weighted average price at which option holders acquired shares when converting their stock options into shares. + References No definition available. + Details
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- Definition Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated. + References No definition available. + 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=109197908&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://fasb.org/us-gaap/role/ref/legacyRef -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=109197908&loc=d3e5070-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -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=115993241&loc=d3e301413-122809 + Details
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- Definition Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, 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 -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Weighted average remaining contractual term for option awards outstanding, 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 (e)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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