Leases - Supplemental Balance Sheet Related to Operating Leases (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Leases [Abstract]
Other current liabilities - operating lease current portion	$ 545	$ 481
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesCurrent	us-gaap:OtherLiabilitiesCurrent
Operating lease liabilities - noncurrent	$ 2,483	$ 2,898
Total operating lease liabilities	$ 3,028	$ 3,379