Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
	Mar. 25, 2020	Mar. 31, 2020	Mar. 31, 2019
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		$ 35	$ 123
Options granted, weighted average grant date fair value (in usd per share)		$ 7.75	$ 12.88
Employee Stock Option | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period (in years)		10 years
Incentive Stock Options And Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares based compensation, vested period (in years)		4 years
Non-Statutory Options | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares based compensation, vested period (in years)		4 years
Non-Statutory Options | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares based compensation, vested period (in years)		3 years
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, restricted stock units granted (in shares)		0
Unrecognized compensation cost of stock based awards		$ 7,000
Unrecognized compensation cost of stock based awards, recognition period		3 years
2017 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Offering period (months)		3 months
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		106,000
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		114,000
Percentage of number of common stock outstanding		4.00%
Proposed Amendment to the 2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of number of common stock outstanding	4.00%
Additional shares authorized (in shares)	474,465
2019 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary share issued (in shares)		400,000
Shares reserved for issuance		137,000