Notes Payable - Summary of Future Principal Payments under Innovatus Loan Agreement (Detail) - Loan and Security Agreement [Member] - Innovatus Life Sciences Lending Fund I, LP [Member] - Term Loan [Member] $ in Thousands	Sep. 30, 2017 USD ($)
Debt Instrument [Line Items]
2019	$ 4,083
2020	7,000
2021	2,917
Total	$ 14,000