Preferred Stock, Common Stock and Stockholders' Equity - Employee Stock Purchase Plan and Stock-Based Compensation - Additional Information (Detail) - USD ($)		1 Months Ended		12 Months Ended
	Jan. 01, 2020	May 31, 2017	Jun. 30, 2013	Dec. 31, 2019	Dec. 31, 2018	Apr. 26, 2018	Apr. 30, 2017
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs				$ 2,100,000
Weighted average period				1 year 2 months 26 days
Aggregate number of shares of common stock reserved under the plan				7,678,152	6,881,051	6,286,425
Shares of common stock available for future issuance under ESPP				263,065	163,065
Stock issued during period, shares, period increase					420,000
Issuance of common stock under employee stock purchase plan				0	28,869
Payroll withholdings from employees					$ 47,000
Amended and Restated ESPP [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate number of shares of common stock reserved under the plan		1,250,000
Increase in number of shares of common stock reserved under the plan		100,000
Number of shares increased annually to common stock shares reserved for issuance		100,000					30,000
Award plan expiration year		2027
Employee stock purchase plan [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price of common stock as percentage of fair market value			85.00%
Percentage of deduction of eligible compensation			20.00%
Aggregate number of shares of common stock reserved under the plan			30,000
Shares available for issuance, description				In addition, the number of shares of common stock available for issuance under the ESPP has been annually increased on the first day of each fiscal year during the term of the ESPP by an amount equal to the lesser of: (i) 30,000 shares; (ii) one percent of the outstanding shares of common stock as of the last day of the immediately preceding fiscal year; or (iii) such other amount as the Company’s board of directors may determine.
Reserve percentage for issuance of shares			1.00%
ESPP approval date			Aug. 29, 2013
Subsequent Event [Member] | Employee stock purchase plan [Member]
Stock-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate number of shares of common stock reserved under the plan	363,065
Stock issued during period, shares, period increase	100,000