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Stock Based Compensation (Awards of Restricted Stock) (Details) - Restricted Stock [Member] | 9 Months Ended
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Sep. 30, 2017 $ / shares shares
Ratably Over Period [Member] | 2/13/2017 | Employee Stock [Member] |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Shares Granted | shares | 1,200
Grant Date Fair Value Per Share | $ / shares | $ 62.53
Vesting Period | Ratably over 5 years from grant date
Ratably Over Period [Member] | 2/16/2017 | Employee Stock [Member] |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Shares Granted | shares | 34,150
Grant Date Fair Value Per Share | $ / shares | $ 63.10
Vesting Period | Ratably over 5 years from grant date
Ratably Over Period [Member] | 3/31/2017 | Employee Stock [Member] |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Shares Granted | shares | 500
Grant Date Fair Value Per Share | $ / shares | $ 65.63
Vesting Period | Ratably over 5 years from grant date
Ratably Over Period [Member] | 4/3/2017 | Employee Stock [Member] |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Shares Granted | shares | 1,500
Grant Date Fair Value Per Share | $ / shares | $ 64.14
Vesting Period | Ratably over 5 years from grant date
Ratably Over Period [Member] | 5/15/2017 | Employee Stock [Member] |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Shares Granted | shares | 1,000
Grant Date Fair Value Per Share | $ / shares | $ 64.03
Vesting Period | Ratably over 5 years from grant date
Ratably Over Period [Member] | 5/23/2017 | Non Employee Director Stock Plan Member |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Grant Date Fair Value Per Share | $ / shares | $ 61.95
Ratably Over Period [Member] | 6/15/2017 | Employee Stock [Member] |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Shares Granted | shares | 950
Grant Date Fair Value Per Share | $ / shares | $ 66.18
Vesting Period | Ratably over 5 years from grant date
At The End of Period [Member] | 5/23/2017 | Non Employee Director Stock Plan Member |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Shares Granted | shares | 7,000
Vesting Period | At the end of 5 years from grant date (1)

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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 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 Net number of non-option equity instruments granted to participants. + 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)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Description of pertinent provisions of equity-based compensation awards that have actual or potential impact upon the company's financial statements. + 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) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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