Leases - Components of lease costs and supplemental information related to leases (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Lease Assets and Liabilities
ROU assets	$ 20,340		$ 19,112
Total lease liabilities	22,237		$ 21,164
Lease Cost
Operating lease expense	1,662	$ 1,623
Sublease income	0	0
Total lease expense	1,662	1,623
Other Information
Operating cash outflows from operating leases, net	$ 1,819	$ 1,935
Lease Term and Discount Rate
Weighted average remaining lease term (years)	4 years 4 months 24 days		4 years 1 month 28 days
Weighted average discount rate	2.63%		2.80%