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Stock-Based Compensation (Tables) | 12 Months Ended
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Dec. 31, 2020
Stock Based Compensation [Abstract] |
Schedule of Share based Payment Award Restricted Stock Valuation Assumptions | The following is a summary of the key assumptions used in the valuation calculations for market based awards granted during the years ended December 31, 2020, 2019 and 2018:
|  | 2020 |  |  | 2019 |  |  | 2018 |
Risk free rate |  | 1.603% |  |  | 2.578% |  |  | 1.61% - 2.14% |
Dividend yield |  | 3.070% |  |  | 4.043% |  |  | 3.884% |
Volatility |  | 17.02% |  |  | 18.95% |  |  | 15.05% - 17.18% |
Requisite service period |  | 3 years |  |  | 3 years |  |  | 3 years |
Nonvested Restricted Stock Shares Activity | A summary of the status of the nonvested restricted shares as of December 31, 2020, and the changes for the year ended December 31, 2020, is presented below:
Nonvested Shares |  | Shares |  |  | Weighted Average Grant-Date Fair Value |
Nonvested as of January 1, 2020 |  |  | 233,878 |  |  | $ | 96.33 |
Issued |  |  | 152,729 |  |  |  | 88.56 |
Vested |  |  | (169,198 | ) |  |  | 81.69 |
Forfeited |  |  | (559 | ) |  |  | 106.86 |
Nonvested as of December 31, 2020 |  |  | 216,850 |  |  | $ | 102.10 |
Share-based Compensation, Stock Options, Activity | A summary of the status of the outstanding stock options as of December 31, 2020 and the changes for the year ended December 31, 2020 is presented below:
Stock Options |  | Options |  |  | Weighted Average Exercise Price |
Outstanding as of January 1, 2020 |  |  | 20,763 |  |  | $ | 77.82 |
Exercised |  |  | (918 | ) |  |  | 77.77 |
Outstanding as of December 31, 2020 |  |  | 19,845 |  |  | $ | 77.83 |

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- Definition Schedule of Share-based Payment Award, Restricted Stock, Valuation Assumptions [Table Text Block] + References No definition available. + Details
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- Definition Tabular disclosure of the changes in outstanding nonvested restricted stock 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 (c) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Tabular disclosure for stock option plans. Includes, but is not limited to, outstanding awards at beginning and end of year, grants, exercises, forfeitures, and weighted-average grant date fair value. + 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) -URI http://asc.fasb.org/extlink&oid=120381028&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 (e) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 Reference 3: 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) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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