Leases - Supplemental Balance Sheet Related to Finance Leases (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Leases [Abstract]
Property and equipment, at cost	$ 371	$ 239
Accumulated amortization	(161)	(52)
Property and equipment, net	210	187
Other current liabilities – finance lease current portion	$ 147	$ 119
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other current liabilities	Other current liabilities
Other long-term liabilities	$ 70	$ 71
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other long-term liabilities	Other long-term liabilities
Total finance lease liabilities	$ 217	$ 190