Stock-Based Compensation - Employee Stock Purchase Plan ("ESPP") - Additional Information (Detail) - Employee Stock Purchase Plan [Member] - USD ($) shares in Thousands, $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Feb. 28, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of fair market value to determine purchase price				85.00%
Offering period				6 months
Proceeds of from issuance of shares under ESPP	$ 0.3	$ 0.4	$ 0.4
Options issued	95,376	77,297	85,483
Rate of discount on fair market value of common stock under ESPP				15.00%
Period of expected life, options granted				5 years