Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended					9 Months Ended	12 Months Ended
	Jun. 04, 2019	Dec. 31, 2019	Jun. 30, 2019	May 31, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2014	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2015	Jan. 01, 2020	Nov. 20, 2019	Jan. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, par value		$ 0.001						$ 0.001	$ 0.001
Compensation expense								$ 10,300	$ 8,401	$ 6,330
Common stock, shares outstanding		46,720,225						46,720,225	39,547,558
Common stock, shares issued		46,720,225						46,720,225	39,547,558
Options granted								1,324,000	1,197,500	1,328,500
Fair value of options granted								$ 11.67	$ 11.99	$ 11.46
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense								$ 5,094	$ 4,482	$ 3,897
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense								5,206	3,919	$ 2,433
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units, vested		36,666		74,166
Director [Member] | Restricted Stock Units [Member] | General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense								287
Executive Officers [Member] | Restricted Stock Units [Member] | General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense								1,180	1,217
Executive Officers [Member] | Restricted Stock Units [Member] | Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense								$ 604	$ 476
Consultants [Member] | Share-based Payment Arrangement, Nonemployee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair values of outstanding options									$ 8.74	$ 10.16
2014 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock options that may be granted after the tenth anniversary of the 2014 Plan								0
Annual increases in number of shares reserved for issuance as a percentage of shares of capital stock outstanding through January 1, 2024											3.00%
Share-based compensation arrangement by share-based payment award, number of shares authorized		6,086,907						6,086,907
2014 Equity Incentive Plan [Member] | Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares authorized												7,488,513
2014 Equity Incentive Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of awards granted									10 years
2014 Equity Incentive Plan [Member] | Maximum [Member] | Incentive Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares authorized											30,000,000
2014 Equity Incentive Plan [Member] | Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards granted									3 years
2014 Equity Incentive Plan [Member] | Director [Member] | Share-based Payment Arrangement, Nonemployee [Member] | Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards granted								1 year
Restricted stock units, approved and granted	24,000							24,000
Restricted stock units, grant date fair value	$ 20.47
Compensation expense								$ 287
Restricted stock units, vested								0
2014 Equity Incentive Plan [Member] | Executive Officers [Member] | Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units, approved and granted					215,000	83,791
Restricted stock units, grant date fair value					$ 16.10	$ 20.21
Compensation expense								$ 1,784	$ 1,693
Restricted stock units, vested		36,666		74,166
Common stock, shares outstanding									83,791
Common stock, shares issued		36,666		74,166				36,666
2014 Equity Incentive Plan [Member] | Executive Officers [Member] | Restricted Stock Units [Member] | General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense								$ 1,180	$ 1,217
2014 Equity Incentive Plan [Member] | Executive Officers [Member] | Restricted Stock Units [Member] | Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense								$ 604	$ 476
2014 Equity Incentive Plan [Member] | Employee And Nonemployee Consultants [Member] | Share-Based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of vested shares on first anniversary of grant date								25.00%
2014 Equity Incentive Plan [Member] | Employee And Nonemployee Consultants [Member] | Share-based Compensation Award, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards granted								36 months
2014 Equity Incentive Plan [Member] | Employee And Nonemployee Consultants [Member] | Share Based Compensation Subsequent Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards granted								4 years
2019 Inducement Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, par value													$ 0.001
2019 Inducement Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, number of shares authorized													300,000
2019 Inducement Plan [Member] | Share-based Payment Arrangement, Employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted								47,500
2019 Inducement Plan [Member] | Share-based Payment Arrangement, Employee [Member] | Share-Based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of vested shares on first anniversary of grant date								25.00%
2019 Inducement Plan [Member] | Share-based Payment Arrangement, Employee [Member] | Share-based Compensation Award, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards granted								36 months
2019 Inducement Plan [Member] | Share-based Payment Arrangement, Employee [Member] | Share Based Compensation Subsequent Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards granted								4 years
Non-employee Director Compensation Policy [Member] | Director [Member] | Share-based Payment Arrangement, Nonemployee [Member] | Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted per director			6,000
2004 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future issuance							0							0
2004 Stock Incentive Plan [Member] | Share-Based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of vested shares on first anniversary of grant date							25.00%
2004 Stock Incentive Plan [Member] | Share-based Compensation Award, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of awards granted							36 months
2004 Stock Incentive Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of awards granted							10 years