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Stock Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Jun. 13, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted		612,050	742,000
Options, Outstanding, Weighted Average Exercise Price		$ 12.04	$ 13.69	$ 128.25
Stock-based compensation expense		$ 2,606	$ 863
Number of common stock available for future grant		1,295,144
Stock-based compensation expense		$ 2,580	$ 863
2018 Omnibus Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted	1,500,000
2018 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum employee subscription rate	15.00%
2018 Employee Stock Purchase Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of fair market value of common stock	85.00%
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term of stock options		6 years 14 days	6 years 10 days
Weighted average grant date fair value of stock options		$ 9.97	$ 4.01
Unrecognized employee stock based compensation expense		$ 6,500
Unrecognized employee stock based compensation expense, period for recognition		2 years 9 months 10 days
Non Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term of stock options			9 years
Options, Grants in Period		0	20,000
Options, Outstanding, Weighted Average Exercise Price			$ 4.69
Stock-based compensation expense		$ 90	$ 20
Non Employee Stock Option | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Vesting Period			1 year
Non Employee Stock Option | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Vesting Period			4 years
2018 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock authorized for issuance		120,000
Number of common stock stock issued		0
Number of common stock available for future grant		120,000
Stock-based compensation expense		$ 30

X

- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Unrecognized cost of unvested options awarded to employees as compensation.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Discount rate from fair value on offering date that participants pay for shares.

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The highest percentage of annual salary that an employee is permitted to utilize with respect to the plan.

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Net number of share options (or share units) granted during the period.

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Gross number of share options (or share units) granted during the period.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Number of share instruments newly issued under a share-based compensation plan.

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Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average grant-date fair value of options vested.

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