Allowance for Credit Losses - Unfunded Loan Commitments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Allowance for loan losses:
Beginning balance	$ 20,535	$ 17,335	$ 20,535	$ 946
(Recovery of) provision for credit losses on unfunded loan commitments (included in other noninterest expense)	(200)	2,700	(200)	8,700
Ending balance	$ 20,335	$ 20,035	20,335	20,035
Cumulative Effect, Period Of Adoption, Adjustment
Allowance for loan losses:
Beginning balance			$ 0	$ 10,389