Share-Based Compensation - Restricted Stock Rollforward (Details)	12 Months Ended
Dec. 31, 2020 $ / shares shares
Restricted Stock LTIP [Member]
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested [Roll Forward]
Beginning Balance \| shares	64,500
Nonvested Stock Awards Granted \| shares	28,244
Nonvested Stock Awards Vested \| shares	(19,195)
Nonvested Stock Awards Forfeited \| shares	(1,781)
Ending Balance \| shares	71,768
Weighted Average Grant Date Fair Value, Nonvested Stock Awards, Beginning of Period \| $ / shares	$ 152.67
Weighted Average Grant Date Fair Value, Nonvested Stock Awards Granted \| $ / shares	145.63
Weighted Average Grant Date Fair Value, Nonvested Stock Awards Vested \| $ / shares	148.15
Weighted Average Grant Date Fair Value, Nonvested Stock Awards Forfeited \| $ / shares	150.27
Weighted Average Grant Date Fair Value, Nonvested Stock Awards, End of Period \| $ / shares	$ 151.17
Restricted Stock Units (RSUs) LTIP Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested [Roll Forward]
Beginning Balance \| shares	8,655
Nonvested Stock Awards Granted \| shares	6,030
Nonvested Stock Awards Vested \| shares	(1,791)
Nonvested Stock Awards Forfeited \| shares	(2,049)
Ending Balance \| shares	10,845
Weighted Average Grant Date Fair Value, Nonvested Stock Awards, Beginning of Period \| $ / shares	$ 152.09
Weighted Average Grant Date Fair Value, Nonvested Stock Awards Granted \| $ / shares	141.65
Weighted Average Grant Date Fair Value, Nonvested Stock Awards Vested \| $ / shares	141.92
Weighted Average Grant Date Fair Value, Nonvested Stock Awards Forfeited \| $ / shares	153.50
Weighted Average Grant Date Fair Value, Nonvested Stock Awards, End of Period \| $ / shares	$ 147.70

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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=120381028&loc=d3e5070-113901

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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

+ 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)(2)(iii)(3)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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- Definition

The number of grants made 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://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)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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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://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)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ 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)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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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.

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- Definition

Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit 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
-Subparagraph (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(2)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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