Stock-Based Compensation and Employee Stock Purchase Program - Additional Information (Detail)					1 Months Ended	3 Months Ended	12 Months Ended
	Aug. 23, 2019	Aug. 22, 2019	May 20, 2015 shares	May 14, 2015	Jun. 30, 2019 shares	Sep. 30, 2018	Dec. 31, 2020 USD ($) IncentivePlan $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity incentive plans | IncentivePlan							2
Total number of options outstanding							889,759	661,701	530,044
Intrinsic value of options exercised | $							$ 0	$ 0
Unrecognized compensation cost related to unvested stock-based compensation grants | $							$ 700,000
Weighted-average remaining recognition period							2 years 9 months 7 days
Stock-based compensation | $							$ 2,042,000	$ 2,287,000
Weighted-average estimated grant-date fair value of stock options granted | $ / shares							$ 3.80	$ 5.13
2015 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total number of shares reserved for issuance under plan							105,036
Stock-based compensation | $							$ 47,000	$ 16,000
Percentage in payroll deductions to acquire shares of common stock				15.00%
Purchase plan offering period				6 months
Employees are able to purchase company's common stock on first trading day of offering period, percentage				85.00%
Issuance of common stock pursuant to employee stock purchase plan							35,056
First offering period, start date				May 14, 2015
First offering period, end date				Feb. 01, 2016
Separation Agreement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable period	2 years	90 days
Separation Agreement [Member] | Selling, General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation | $								$ 438,000
2015 Omnibus Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Terms under the plan							The 2015 Plan became effective upon the Company’s IPO in May 2015 and all shares that were reserved, but not issued, under the 2006 Plan were assumed by the 2015 Plan. Upon effectiveness, the 2015 Plan had 154,387 shares of common stock reserved for future issuance, which included 10,637 that were transferred to and assumed by the 2015 Plan. The 2015 Plan provides for automatic annual increases in shares available for grant. In addition, shares subject to awards under the 2006 Plan that are forfeited or canceled will be added to the 2015 Plan.
Total number of shares reserved for issuance under plan			154,387				1,047,243
Options vesting period			4 years			2 years
Additional shares authorized for issuance under the plan					120,000
Common stock available for future grant							157,484
Total number of options outstanding							870,587	616,472
2006 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total number of shares reserved for issuance under plan			10,637
Total number of options outstanding							19,172	45,229
Maximum [Member] | 2015 Omnibus Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercisable period			10 years