Leases - Supplemental balance sheet information related to leases (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Operating Leases:
Operating lease right-of-use assets	$ 13,713	$ 12,521
Operating lease liabilities	$ 13,935	$ 12,690
Operating Lease, Liability, Statement of Financial Position [Extensible List]	us-gaap:OperatingLeaseLiability
Weighted Average Remaining Lease Term:
Operating Leases	10 years	11 years
Weighted Average Discount Rate:
Operating Leases	3.10%	3.50%