Stock-Based Compensation - Time-Based Restricted Stock and Restricted Stock Unit Activity (Detail) - Time-Based Restricted Stock and Time-Based Restricted Stock Units [Member] - $ / shares	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Restricted Stock Activity [Line Items]
Nonvested, Shares, Beginning Balance	155,548	153,118	243,600
Time-based Restricted Stock, Granted	35,650	87,264	72,402
Time-based Restricted Stock, Vested	(81,325)	(84,550)	(162,372)
Time-based Restricted Stock, Forfeited	(640)	(284)	(512)
Nonvested, Shares, Ending Balance	109,233	155,548	153,118
Nonvested, Weighted-Average Grant Price Per Share, Beginning Balance	$ 42.68	$ 26.90	$ 15.80
Weighted-Average Grant Price Per Share, Granted	76.23	54.72	36.27
Weighted-Average Grant Price Per Share, Vested	37.34	26.65	14.45
Weighted-Average Grant Price Per Share, Forfeited	62.33	35.05	18.68
Nonvested, Weighted-Average Grant Price Per Share, Ending Balance	$ 57.49	$ 42.68	$ 26.90

Schedule of restricted stock activity.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited 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)(1)(iv)(3)
-URI http://asc.fasb.org/extlink&oid=116856206&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)
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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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(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

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-Publisher FASB
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-Topic 718
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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.

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-Name Accounting Standards Codification
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-SubTopic 10
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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.

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-Publisher FASB
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- Definition

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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