Stock-Based Compensation - Stock Options - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercised	19,606	73,680
Intrinsic value based on share price	$ 6.57
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee stock options vesting provisions, description	Employee options are subject to installment vesting and although the vesting may vary from year to year, it is typically over a period of three years.
Options vested in remaining period	3 years
Period of termination of employment	180 days
Stock options granted period	10 years
Options Granted	0	0
Options exercised	61,767	154,409
Intrinsic value	$ 0.1	$ 0.2
Lower range of exercise prices	$ 5.06
Upper range of exercise prices	$ 8.21
Period of expected life, options granted	5 years
Stock Options [Member] | Stock Option Plan One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from options exercised	$ 0.1	$ 0.5
Options exercised	9,412	62,909
Stock Options [Member] | Stock Option Plan Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercised	52,355	91,500
Shares issued	10,194	10,771