Share-based Compensation - Summary of Non-vested Restricted Share Activity (Details)	12 Months Ended
Dec. 31, 2018 $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Numbers of non-vested restricted shares, Beginning Balance \| shares	693,333
Numbers of non-vested restricted shares, Granted \| shares	757,000
Numbers of non-vested restricted shares, Vested \| shares	(338,332)
Numbers of non-vested restricted shares, Ending Balance \| shares	1,112,001
Weighted average grant date fair value, Beginning Balance \| $ / shares	$ 2.57
Weighted average grant date fair value, Granted \| $ / shares	20.73
Weighted average grant date fair value, Vested \| $ / shares	1.95
Weighted average grant date fair value, Ending Balance \| $ / shares	$ 15.13

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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://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)(1)
-URI http://asc.fasb.org/extlink&oid=109197908&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

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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.

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

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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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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