Stockholders' Equity - Additional information (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
	Apr. 15, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jul. 25, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to non-vested share-based compensation awards granted		$ 5,600		$ 5,600
Unrecognized compensation cost related to non-vested share-based compensation awards granted year				2022
Stock option exercisable (in shares)		1,903,370		1,903,370
Proceeds from issuance common stock before underwriters discounts and commissions and offering expenses	$ 50,000
Proceeds from issuance common stock net of underwriters discounts and commissions and offering expenses	47,600
Gross proceeds to selling stockholder from public offering	$ 19,000			$ 48,000	$ 0
Stock options granted to underwriters vesting period	30 days
Common Stock, shares authorized (in shares)		175,000,000		175,000,000			125,000,000
Common stock, capital shares reserved for future issuance (in shares)						14,000,000
Series B issuance, net of issuance costs (in shares)	12,000,000
Sale of stock, price per share (in dollars per share)	$ 5.00
Sale of stock, number of shares issued in transaction (in shares)	10,000,000
Antidilutive shares excluded from the computation of diluted earnings per common share (in shares)		15,488,972	25,745,108	15,260,949	18,917,774
IPO
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted to underwriters number of shares in grant after underwriter expenses (in shares)	1,800,000
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity instruments awarded in period (in shares)				360,250
Vesting period of shares				3 years
Fair market value of RSUs granted				$ 1,600
Series B Preferred Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion of Series A preferred stock (in shares)		(18)	(1,900)	(1,402)	(1,900)
Series A preferred shares outstanding (in shares)		1,698		1,698			3,100
Series B issuance, net of issuance costs (in shares)					5,000
Series A Preferred Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Series A preferred shares outstanding (in shares)		2,093,155		2,093,155			2,093,155
Series B issuance, net of issuance costs (in shares)				0
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion of Series A preferred stock (in shares)		100,000	10,555,556	7,788,888	10,555,556
Board of Directors and Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity instruments awarded in period (in shares)				2,267,904
Fair market value of shares granted				$ 9,500
Term of options granted period				10 years
Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of shares				3 years
Employees | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity instruments awarded in period (in shares)				47,000
Board of Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of shares, description				Board of Directors vest ratably through 2022