Long-term debt - Schedule Of Maturities Of Long Term Debt (Detail) $ in Thousands	Sep. 30, 2019 USD ($)
Debt Instrument [Line Items]
2020	$ 3,333
2021	3,333
2022	834
Long-term Debt	7,500
2020	486
2021	214
2022	11
Interest Payable On Long Term Debt	711
2020	3,819
2021	3,547
2022	845
Long Term Debt Maturities Repayment Principal And Interest Total	8,211
Less: Interest	711
Long-term Debt	7,500
Less unamortized debt discount	(269)
Add: accretion of final payment fee	502
Long Term Debt Including Interest And Fee Payable	7,733
Accrued Expenses [Member]
Debt Instrument [Line Items]
Interest Payable On Long Term Debt	(711)
Less: Interest	$ (711)