Equity - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended	9 Months Ended
	Aug. 31, 2019	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Class of Stock [Line Items]
Common stock, shares authorized		200,000,000	200,000,000		200,000,000
Common stock, par value		$ 0.0001	$ 0.0001		$ 0.0001
Issuance of stock, issuance costs				$ 3,524,000
Jefferies Sales Agreement [Member]
Class of Stock [Line Items]
Proceeds from issuance of common shares			$ 145,000
Issuance of stock, issuance costs		$ 200,000	$ 200,000
Maximum [Member] | Jefferies Sales Agreement [Member]
Class of Stock [Line Items]
Gross proceeds from issuance of common shares	$ 50,000,000
Common Stock [Member] | Jefferies Sales Agreement [Member]
Class of Stock [Line Items]
Shares issued		39,506	39,506
Proceeds from issuance of common shares		$ 100,000	$ 100,000
Issuance of stock, issuance costs		$ 200,000	$ 200,000
Commission, percentage of gross proceeds of common stock	3.00%