Description of basis for conversion of convertible common stock.

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Equity Incentive Plan - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jun. 03, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Tax effect for stock-based compensation benefit (expense) for option and restricted stock units exercised	$ 11	$ (49)	$ 177
Employee Stock Options And Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Tax effect for stock-based compensation benefit (expense) for option and restricted stock units exercised	$ 2,188	$ 3,446	$ 2,211
2005 Equity Incentive Plan \| Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion ratio of restricted stock unit to ordinary shares	one-for-one
2015 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary shares authorized				20,000,000
The 2005 Plan and The 2015 Plan \| Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost related to non-vested share-based compensation	$ 3,116