Summary of Restricted Stock Activity (Detail) - Restricted Stock Units (RSUs) - $ / shares	4 Months Ended	5 Months Ended	12 Months Ended
Jul. 31, 2017	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Time Based Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average Grant-Date Fair Value, Beginning Balance Outstanding	$ 54.48		$ 24.21	$ 24.41
Weighted-average Grant-Date Fair Value, Granted		$ 24.40	23.44	24.58
Weighted-average Grant-Date Fair Value, Vested	$ 54.48		24.45	24.84
Weighted-average Grant-Date Fair Value, Cancelled/forfeited		24.15	24.70	27.15
Weighted-average Grant-Date Fair Value, Ending Balance Outstanding		$ 24.41	$ 23.32	$ 24.21
Number of Shares Beginning Balance Outstanding	183		1,081,084	1,157,646
Number of Shares, Granted		1,203,379	186,143	455,063
Number of Shares, Vested	(183)		(784,868)	(503,677)
Number of Shares, Cancelled/forfeited		(45,733)	(78,591)	(27,948)
Number of Shares Ending Balance Outstanding		1,157,646	403,768	1,081,084
Performance Based Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average Grant-Date Fair Value, Beginning Balance Outstanding			$ 26.04
Weighted-average Grant-Date Fair Value, Granted			24.50	$ 26.04
Weighted-average Grant-Date Fair Value, Cancelled/forfeited			24.50
Weighted-average Grant-Date Fair Value, Ending Balance Outstanding			$ 25.54	$ 26.04
Number of Shares Beginning Balance Outstanding			63,365
Number of Shares, Granted			101,143	63,365
Number of Shares, Cancelled/forfeited			(70,694)
Number of Shares Ending Balance Outstanding			93,814	63,365

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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
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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.

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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).

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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).

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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.

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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.

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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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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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- 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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