Commitments and Contingencies - University of California License Agreements - Additional Information (Detail) - University of California License Agreements [Member] - USD ($)		1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended		28 Months Ended
	Dec. 31, 2015	Jun. 30, 2015	Sep. 30, 2017	Sep. 30, 2017	Dec. 31, 2016	Dec. 31, 2015	Sep. 30, 2017
Commitments And Contingencies [Line Items]
Upfront payment		$ 50,000
Annual license maintenance fee						$ 15,000
Research and development expense related to milestone expense			$ 0	$ 0	$ 0
Milestone payments			$ 0	$ 0	$ 0
After The Effective Date [Member]
Commitments And Contingencies [Line Items]
Licenses Expiration period, maximum	27 years
After The First Sale [Member]
Commitments And Contingencies [Line Items]
Licenses Expiration period, maximum	15 years
Clinical Development [Member]
Commitments And Contingencies [Line Items]
Milestone payments	$ 100,000
Clinical Development [Member] | Maximum [Member]
Commitments And Contingencies [Line Items]
Percentage of net sales paid as royalties	1.00%
Regulatory Milestones [Member] | Maximum [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments		700,000
Additional milestone payments							$ 0
Sales Milestones [Member] | Maximum [Member]
Commitments And Contingencies [Line Items]
Expected milestone payments		$ 2,000,000
Additional milestone payments							$ 0