Stock Based Compensation (Awards of Restricted Stock) (Details) - Restricted Stock [Member]	9 Months Ended
Sep. 30, 2019 $ / shares shares
Ratably Over Period [Member] \| 2/21/2019 \| Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Granted \| shares	43,250
Grant Date Fair Value Per Share \| $ / shares	$ 83.87
Vesting Period	Ratably over 5 years from grant date
Ratably Over Period [Member] \| 3/15/2019 \| Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Granted \| shares	600
Grant Date Fair Value Per Share \| $ / shares	$ 79.55
Vesting Period	Ratably over 5 years from grant date
Ratably Over Period [Member] \| 4/01/2019 \| Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Granted \| shares	1,090
Grant Date Fair Value Per Share \| $ / shares	$ 82.62
Vesting Period	Ratably over 3 years from grant date
Immediate Vest on grant date [Member] \| 5/21/2019 \| Two Thousand Eighteen Nonemployee Director Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Granted \| shares	6,500
Grant Date Fair Value Per Share \| $ / shares	$ 77.08
Vesting Period	Shares vested immediately

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).

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)(2)(iii)(1)
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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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