Commitments and Contingencies - Washington University License Agreement - Additional Information (Detail) - Washington University License Agreement [Member] - USD ($)	1 Months Ended	12 Months Ended
	Nov. 30, 2013	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2013
Commitments And Contingencies [Line Items]
Upfront non-refundable payment	$ 50,000
Annual license maintenance fee					$ 15,000
Issuance of common stock, shares					47,619
Research and development expense related to issue of common stock obligation					$ 100,000
Research and development expense related to milestone expense		$ 0	$ 0	$ 0
Milestone payments		0	$ 0	$ 0
Clinical Development [Member]
Commitments And Contingencies [Line Items]
Research and development expense related to milestone expense		50,000
Milestone payments		$ 50,000
Maximum [Member] | Clinical Development [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments	700,000
Maximum [Member] | Regulatory Milestones [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments	$ 500,000