Stock-Based Compensation - Additional Information (Detail) $ / shares in Units, $ in Thousands	9 Months Ended
Sep. 30, 2019 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum percentage of fair market value of common stock	100.00%
Aggregate intrinsic value, options exercised \| $	$ 184
Options granted, weighted average grant date fair value (in usd per share) \| $ / shares	$ 11.33
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, restricted stock units granted (in shares)	116,689
Restricted stock units vested, percentage	25.00%
Shares based compensation, vested period (in years)	4 years
Share based compensation, grant date fair value \| $	$ 1,700
Unrecognized compensation cost of stock based awards \| $	$ 6,700
Unrecognized compensation cost of stock based awards, recognition period	3 years 2 months 12 days
2017 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock issued (in shares)	0
2015 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary share issued (in shares)	969,340
Shares reserved for issuance	73,000
2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary share issued (in shares)	170,915
Shares reserved for issuance	20,000
Percentage of number of common stock outstanding	4.00%
2019 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary share issued (in shares)	150,000
Shares reserved for issuance	55,000

Aggregate number of common shares reserved for future issuance.

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Unrecognized cost of unvested share-based compensation awards.

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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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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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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).

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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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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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Maximum number of shares that may be issued in accordance with the plan as a proportion of outstanding capital stock.

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

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Percentage of restricted stock units vesting.

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