Summary of Operating Lease Assets and Liabilities (Detail) $ in Thousands	Sep. 30, 2019 USD ($)
Assets And Liabilities Lessee [Abstract]
Operating lease assets	$ 4,400
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsMember
Operating lease liabilities, current	$ 698
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherCurrentLiabilitiesMember
Operating lease liabilities, noncurrent	$ 4,135
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherNoncurrentLiabilitiesMember
Total lease liabilities	$ 4,833