Sole-Source Cost-Sharing Agreement and Cooperative Research and Development Agreement - Additional Information (Detail) - USAMRMC - USD ($)		1 Months Ended	3 Months Ended	12 Months Ended
	Nov. 07, 2017	Jul. 31, 2015	Sep. 30, 2017	Dec. 31, 2017
Schedule Of Cost Sharing Agreement And Cooperative Research And Development Agreement [Line Items]
Expiration date of original contract				Dec. 31, 2016
Reimbursement received				$ 3,000,000
Reimbursement received recorded as advance against final milestone				$ 200,000
Extended expiration date of original contract	Dec. 31, 2018
Maximum
Schedule Of Cost Sharing Agreement And Cooperative Research And Development Agreement [Line Items]
Reimbursable trial cost		$ 3,000,000
Cooperative Research and Development Agreement
Schedule Of Cost Sharing Agreement And Cooperative Research And Development Agreement [Line Items]
Extended expiration date of original contract			Dec. 31, 2021
Expiration year of original contract			2018