Incentive Plan - Summary of Granted but Unvested Stock Award Activity (Detail) - $ / shares	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Number of Shares, Outstanding at beginning of year (shares)	330,598	169,703	156,945
Number of Shares, Granted (shares)	249,651	272,668	69,175
Number of Shares, Vested (shares)	(105,307)	(58,754)	(47,379)
Number of Shares, Forfeited (shares)	(23,499)	(53,019)	(9,038)
Number of Shares, Outstanding at end of year (shares)	451,443	330,598	169,703
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted Average Grant Date Fair Value, Outstanding at beginning of year (usd per share)	$ 25.92	$ 21.79	$ 17.25
Weighted Average Grant Date Fair Value, Granted (usd per share)	24.80	27.52	28.70
Weighted Average Grant Date Fair Value, Vested (usd per share)	24.49	20.81	17.32
Weighted Average Grant Date Fair Value, Forfeited (usd per share)	26.38	26.60	19.14
Weighted Average Grant Date Fair Value, Outstanding at end of year (usd per share)	$ 25.61	$ 25.92	$ 21.79

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=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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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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
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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

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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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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- Definition

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

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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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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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-Publisher FASB
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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.

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No definition available.

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