Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands								1 Months Ended				12 Months Ended
	Aug. 20, 2019	Jul. 29, 2019	Mar. 20, 2019	Jul. 23, 2018	Jul. 18, 2018	Apr. 05, 2017	Mar. 30, 2017	Dec. 31, 2019	Jul. 31, 2019	May 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Apr. 04, 2019
Subsidiary Sale Of Stock [Line Items]
Common stock, shares authorized								100,000,000			100,000,000	100,000,000	100,000,000
Common stock, par value								$ 0.001			$ 0.001	$ 0.001	$ 0.001
Preferred stock, shares authorized								5,000,000			5,000,000	5,000,000	5,000,000
Preferred stock, par value								$ 0.001			$ 0.001	$ 0.001	$ 0.001
Common stock, shares outstanding								46,720,225			39,547,558	46,720,225	39,547,558
Common stock, shares issued								46,720,225			39,547,558	46,720,225	39,547,558
Preferred stock, shares issued								0			0	0	0
Preferred Stock Shares Outstanding								0			0	0	0
Restricted stock units vested shares											83,791
Unregistered common stock exchanged for consulting services												$ 197
Compensation expense												10,300	$ 8,401	$ 6,330
Shareholder Consulting Agreement [Member]
Subsidiary Sale Of Stock [Line Items]
Price per share			$ 19.37
Number of shares of unregistered common stock exchanged for consulting services			10,195
Consulting services performance period			6 months
General and Administrative [Member]
Subsidiary Sale Of Stock [Line Items]
Compensation expense												5,094	$ 4,482	$ 3,897
General and Administrative [Member] | Shareholder Consulting Agreement [Member]
Subsidiary Sale Of Stock [Line Items]
Compensation expense												$ 197
Non-Exclusive License Agreement
Subsidiary Sale Of Stock [Line Items]
Upfront fee	$ 8,000
Upfront fee payable, cash	4,000
Upfront fee payable, stock	$ 4,000
Price per share	$ 23.42
Share price average, Determination period	30 days
Percentage of payment, stock	50.00%
Maximum [Member]
Subsidiary Sale Of Stock [Line Items]
Aggregate offering price of securities															$ 300,000
Follow-on Public Offering [Member]
Subsidiary Sale Of Stock [Line Items]
Price per share								$ 23.00			$ 19.00	$ 23.00	$ 19.00	$ 18.00
Common Stock [Member]
Subsidiary Sale Of Stock [Line Items]
Restricted stock units vested shares								36,666		74,166		110,832	83,791
Common stock, shares issued												6,325,000	5,175,000	5,117,500
Number of shares of unregistered common stock exchanged for consulting services												10,195
Common Stock [Member] | Non-Exclusive License Agreement
Subsidiary Sale Of Stock [Line Items]
Upfront fee payable, stock	$ 4,000
Common stock, shares issued	170,793
Common Stock [Member] | Follow-on Public Offering [Member]
Subsidiary Sale Of Stock [Line Items]
Common stock, shares issued									6,325,000
Common stock, shares issued					5,175,000		5,117,500
Price per share					$ 19.00		$ 18.00		$ 23.00
Proceeds from issuance of common stock net of underwriting discounts, commissions and estimated offering expenses		$ 136,498
Proceeds from issuance of common stock net of underwriting discounts and offering costs				$ 92,063		$ 86,224
Common Stock [Member] | Underwriter's Over-Allotment [Member]
Subsidiary Sale Of Stock [Line Items]
Common stock, shares issued		825,000		675,000	675,000	667,500	667,500		825,000
Underwriting discounts, commission and offering expenses		$ 8,977		$ 6,262		$ 5,891