Share-Based Compensation - Summary of RSUs (Detail)	12 Months Ended
Dec. 31, 2020 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested as of January 1, 2020	211,634
Granted	81,086
Vested	(79,343)
Forfeited	(13,814)
Nonvested as of December 31, 2020	199,563
Nonvested as of January 1, 2019, Weighted-Average Grant-Date Fair Value \| $ / shares	$ 53.68
Weighted-Average Grant-Date Fair Value, Granted \| $ / shares	54.25
Weighted-Average Grant-Date Fair Value, Vested \| $ / shares	56.13
Weighted-Average Grant-Date Fair Value, Forfeited \| $ / shares	61.29
Nonvested as of December 31, 2019, Weighted-Average Grant- Date Fair Value \| $ / shares	$ 60.33
Performance and Service Required [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested as of January 1, 2020	196,342
Granted	71,539
Vested	(73,053)
Forfeited	(11,051)
Nonvested as of December 31, 2020	183,777
Service Required [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested as of January 1, 2020	15,292
Granted	9,547
Vested	(6,290)
Forfeited	(2,763)
Nonvested as of December 31, 2020	15,786

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

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-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

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-Publisher FASB
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-Topic 718
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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

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

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-Publisher FASB
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-Topic 718
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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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-Publisher FASB
-Name Accounting Standards Codification
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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.

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-Publisher FASB
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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.

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No definition available.

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