Lease Commitments and Contingencies - Summary of Lease Cost (Detail) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2021 USD ($)
Lease, Cost [Abstract]
Amortization of right-of-use asset	$ 14	$ 43
Interest expense	2	6
Total lease cost	$ 16	$ 49
Weighted-average remaining term (years)	13 years 1 month 6 days	13 years 1 month 6 days
Weighted-average discount rate	4.90%	4.90%