Premises and Equipment - Narrative (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Leases [Abstract]
Lease liability	$ 17,100	$ 18,400
Operating lease liability	16,987	18,300
Finance lease liability	70	200
Right-of-use asset	18,200	17,700
Operating lease, right of use asset	17,800	17,500
Finance lease, right of use asset	$ 400	$ 200
Finance lease, weighted average remaining lease term (in years)	1 year 10 months 24 days	2 years 3 months 18 days
Finance lease, weighted average discount rate, (as a percentage)	2.10%	2.40%
Operating lease, weighted average remaining lease term (in years)	12 years 2 months 12 days	12 years 10 months 24 days
Operating lease, weighted average discount rate, (as a percentage)	2.80%	2.90%