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Equity-Based Compensation - Summarizes Information Related to Awards (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested shares outstanding at December 31, beginning balance	3,980,773
Granted, shares	1,639,560
Vested, shares	(1,676,735)
Forfeited, shares	(201,700)
Non-vested shares outstanding at December 31, ending balance	3,741,898	3,980,773
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Non-vested shares outstanding at December 31, beginning balance, weighted average grant date fair value per share (in dollars per share)	$ 9.48
Granted, weighted average grant date fair value per share (in dollars per share)	15.03	$ 5.63	$ 14.28
Vested, weighted average grant date fair value per share (in dollars per share)	11.81
Forfeited, weighted average grant date fair value per share (in dollars per share)	10.99
Non-vested shares outstanding at December 31, ending balance, weighted average grant date fair value per share (in dollars per share)	$ 10.78	$ 9.48
Performance share unit awards
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested shares outstanding at December 31, beginning balance	1,387,619
Granted, shares	509,800
Vested, shares	0
Forfeited, shares	(24,709)
Non-vested shares outstanding at December 31, ending balance	1,872,710	1,387,619
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Non-vested shares outstanding at December 31, beginning balance, weighted average grant date fair value per share (in dollars per share)	$ 9.52
Granted, weighted average grant date fair value per share (in dollars per share)	16.89	$ 3.00	$ 11.20
Vested, weighted average grant date fair value per share (in dollars per share)	0.00
Forfeited, weighted average grant date fair value per share (in dollars per share)	42.01
Non-vested shares outstanding at December 31, ending balance, weighted average grant date fair value per share (in dollars per share)	$ 11.10	$ 9.52
Phantom units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested shares outstanding at December 31, beginning balance	0
Granted, shares	101,500
Vested, shares	0
Forfeited, shares	(2,400)
Non-vested shares outstanding at December 31, ending balance	99,100	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Non-vested shares outstanding at December 31, beginning balance, weighted average grant date fair value per share (in dollars per share)	$ 0.00
Granted, weighted average grant date fair value per share (in dollars per share)	16.40
Vested, weighted average grant date fair value per share (in dollars per share)	0.00
Forfeited, weighted average grant date fair value per share (in dollars per share)	16.40
Non-vested shares outstanding at December 31, ending balance, weighted average grant date fair value per share (in dollars per share)	$ 16.40	$ 0.00
Restricted unit awards
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested shares outstanding at December 31, beginning balance	0
Granted, shares	11,766
Vested, shares	0
Forfeited, shares	0
Non-vested shares outstanding at December 31, ending balance	11,766	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Non-vested shares outstanding at December 31, beginning balance, weighted average grant date fair value per share (in dollars per share)	$ 0.00
Granted, weighted average grant date fair value per share (in dollars per share)	17.00
Vested, weighted average grant date fair value per share (in dollars per share)	0.00
Forfeited, weighted average grant date fair value per share (in dollars per share)	0.00
Non-vested shares outstanding at December 31, ending balance, weighted average grant date fair value per share (in dollars per share)	$ 17.00	$ 0.00

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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- 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://www.xbrl.org/2003/role/presentationRef
-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
-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 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

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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- Definition

The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

+ 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

The number of equity-based payment instruments, excluding stock (or unit) options, that vested 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)(2)(iii)(2)
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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
-Name Accounting Standards Codification
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