Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Additional Information (Details 2)	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) KeyRatio	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Financing Receivable Recorded Investment [Line Items]
Number of days used as baseline in evaluating collateral documentation exceptions for loan policy			90 days
Number of key quality ratios | KeyRatio			6
Exposure for commercial non accrual loans to be reviewed on individual basis	$ 500,000		$ 500,000
Exposure for commercial accrual loans deemed to be reviewed on individual basis	500,000		500,000
LHFS past due 90 days or more	75,100,000		$ 75,100,000		$ 119,400,000
Percentage of outstanding principal to be repurchased under GNMA optional repurchase program			100.00%
Financing Receivable [Abstract]
PCL	(2,492,000)	$ 1,760,000	$ (16,984,000)	$ 40,526,000
Allowance for Credit Losses, ACL [Member]
Financing Receivable [Abstract]
PCL	(2,492,000)	1,760,000	(16,984,000)	40,526,000
Allowance for Credit Losses, ACL [Member] | Commercial and Industrial Loans [Member]
Financing Receivable [Abstract]
PCL	3,377,000	232,000	4,257,000	(3,700,000)
Allowance for Credit Losses, ACL [Member] | State and Other Political Subdivision Loans [Member]
Financing Receivable [Abstract]
PCL	(269,000)	(456,000)	(226,000)	(1,726,000)
Allowance for Credit Losses, ACL [Member] | Other Commercial Loans [Member]
Financing Receivable [Abstract]
PCL	(1,989,000)	$ 1,060,000	(2,830,000)	$ 217,000
Minimum [Member]
Financing Receivable [Abstract]
Credit amount used as baseline in evaluating loan policy	$ 100,000		$ 100,000