Leases - Supplemental Balance Sheet Related to Operating Leases (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Leases [Abstract]
Other current liabilities - operating lease current portion	$ 649	$ 568
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other current liabilities	Other current liabilities
Operating lease liabilities - noncurrent	$ 2,019	$ 2,330
Total operating lease liabilities	$ 2,668	$ 2,898