Leases - (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021 USD ($) lease	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) lease	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Net gain on disposition of assets			$ 621,000	$ 0
Short-term lease expense	$ 34,000	$ 34,000	129,000		$ 102,000
Variable lease payments			800,000	800,000
Operating lease cost	$ 2,217,000	1,895,000	$ 6,565,000	5,700,000	$ 5,676,000
Weighted-average remaining lease term-operating leases (Year)	7 years 6 months		7 years 6 months		8 years 3 months 18 days
Weighted average discount rate-operating leases	3.20%		3.20%		3.20%
Minimum [Member]
Term of contract	1 month		1 month
Maximum [Member]
Term of contract	15 years		15 years
Branches And Office Space [Member]
Number of leases | lease	28		28
Vehicles [Member]
Number of leases | lease	10		10
Equipment [Member]
Number of leases | lease	1		1
Professional Services [Member]
Short-term lease expense		$ 34,000	$ 129,000	$ 102,000