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Stock Option and Incentive Plan Schedule of Stock Options Status (Details) - $ / shares | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] |  |  |
Beginning Outstanding, Shares | 547,129 | 547,129 | 553,312
Beginning Oustanding, Weighted Average Exercise Price | $ 96.38 | $ 96.38 | $ 97.21
Exercised, Shares | (6,688) | 0 | (11,447)
Exercised, Weighted Averge Exercise Price | $ 99.15 | $ 0.00 | $ 92.50
Special dividend adjustment (shares) |  |  | 5,264
Special dividend adjustment weighted average exercise price |  |  | $ 96.38
Ending Outstanding, Shares | 540,441 | 547,129 | 547,129
Ending Oustanding, Weighted Average Exercise Pric | $ 96.35 | $ 96.38 | $ 96.38

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- Definition Number of options outstanding, including both vested and non-vested options. + 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=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -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=6415400&loc=d3e5070-113901 + Details
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