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Summary of Restricted Stock Activity (Detail) - $ / shares	4 Months Ended	5 Months Ended	12 Months Ended
	Jul. 31, 2017	Dec. 31, 2017	Mar. 31, 2017
Predecessor
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average Grant-Date Fair Value, Beginning Balance Outstanding	$ 24.19		$ 23.58
Weighted-average Grant-Date Fair Value, Ending Balance Outstanding			$ 24.19
Number of Shares Beginning Balance Outstanding	350,838		363,630
Number of Shares Ending Balance Outstanding			350,838
Restricted Stock Units (RSUs) | Time Based Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average Grant-Date Fair Value, Granted		$ 24.40
Weighted-average Grant-Date Fair Value, Cancelled/forfeited		24.15
Weighted-average Grant-Date Fair Value, Ending Balance Outstanding		$ 24.41
Number of Shares, Granted		1,203,379
Number of Shares, Cancelled/forfeited		(45,733)
Number of Shares Ending Balance Outstanding		1,157,646
Restricted Stock Units (RSUs) | Time Based Shares | Predecessor
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average Grant-Date Fair Value, Beginning Balance Outstanding	$ 54.48		$ 49.17
Weighted-average Grant-Date Fair Value, Vested	$ 54.48		49.39
Weighted-average Grant-Date Fair Value, Cancelled/forfeited			49.62
Weighted-average Grant-Date Fair Value, Ending Balance Outstanding			$ 54.48
Number of Shares Beginning Balance Outstanding	183		89,639
Number of Shares, Vested	(183)		(76,006)
Number of Shares, Cancelled/forfeited			(13,450)
Number of Shares Ending Balance Outstanding			183
Restricted Stock Units (RSUs) | Performance Based Shares | Predecessor
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average Grant-Date Fair Value, Beginning Balance Outstanding			$ 61.75
Weighted-average Grant-Date Fair Value, Cancelled/forfeited			$ 61.75
Number of Shares Beginning Balance Outstanding			156,851
Number of Shares, Cancelled/forfeited			(156,851)

X

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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=96867065&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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(3)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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-Paragraph 2
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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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=96867065&loc=d3e5070-113901

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- Definition

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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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