Share-Based Compensation - Summary of Activity Related to RSU Awards (Detail) - Restricted Stock Units [Member]	9 Months Ended
Sep. 30, 2018 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Awards outstanding, Beginning balance \| shares	35,000
Number of Shares, Vested \| shares	(11,667)
Number of Shares, Awards outstanding, Ending balance \| shares	23,333
Number of Shares, RSUs expected to vest \| shares	22,896
Weighted-Average Grant Date Fair Value, Awards outstanding, Beginning balance \| $ / shares	$ 5.81
Weighted-Average Grant Date Fair Value, Vested \| $ / shares	5.81
Weighted-Average Grant Date Fair Value, Awards outstanding, Ending balance \| $ / shares	5.81
Weighted-Average Grant Date Fair Value, RSUs expected to vest \| $ / shares	$ 5.81

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.

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)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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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.

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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://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)(2)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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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.

+ 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)(2)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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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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No definition available.

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- Definition

Share based compensation arrangement by share based payment award equity instruments other than options expected to vest outstanding number.

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No definition available.

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- Definition

Share based compensation arrangement by share based payment award equity instruments other than options expected to vest weighted average grant date fair value.

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