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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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
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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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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-Paragraph 2
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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
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-Paragraph 2
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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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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

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)(2)
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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

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

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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.

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- Definition

Number of shares used to settle grantee's tax withholding obligation for award under share-based payment arrangement.

+ References

No definition available.

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Share-Based Compensation and Benefit Plans (Summary of Restricted Stock) (Details) - Restricted stock [Member] - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-Based Compensation and Benefit Plans
Restricted stock granted during period, weighted-average grant date fair value	$ 412.67	$ 355.91	$ 263.89
Employee [Member]
Share-Based Compensation and Benefit Plans
Non-vested restricted stock at beginning of the year, weighted-average grant date fair value	301.40
Restricted stock granted during period, weighted-average grant date fair value	419.88
Restricted stock vested during the period, weighted-average grant date fair value	289.03
Restricted stock forfeited during the period, weighted-average grant date fair value	0
Non-vested restricted stock at the end of the year, weighted-average grant date fair value	$ 358.58	$ 301.40
Employee [Member] \| Performance shares [Member]
Share-Based Compensation and Benefit Plans
Non-vested restricted stock beginning balance, shares	4
Restricted stock granted during the period, shares	2
Restricted stock vested during the period, shares	(2)
Restricted stock forfeited during the period, shares	0
Non-vested restricted stock ending balance, shares	4	4
Shares withheld to cover employees' taxes upon vesting	1
Director [Member]
Share-Based Compensation and Benefit Plans
Non-vested restricted stock at beginning of the year, weighted-average grant date fair value	$ 312.96
Restricted stock granted during period, weighted-average grant date fair value	407.12
Restricted stock vested during the period, weighted-average grant date fair value	293.72
Restricted stock forfeited during the period, weighted-average grant date fair value	0
Non-vested restricted stock at the end of the year, weighted-average grant date fair value	$ 371.46	$ 312.96
Director [Member] \| Performance shares [Member]
Share-Based Compensation and Benefit Plans
Non-vested restricted stock beginning balance, shares	4
Restricted stock granted during the period, shares	2
Restricted stock vested during the period, shares	(2)
Restricted stock forfeited during the period, shares	0
Non-vested restricted stock ending balance, shares	4	4