Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Additional Information (Details 2)	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) KeyRatio	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Financing Receivable, Recorded Investment, Aging [Abstract]
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	81,500,000		$ 81,500,000		$ 119,400,000
Percentage of outstanding principal to be repurchased under GNMA optional repurchase program			100.00%
Financing Receivable [Abstract]
PCL	(3,991,000)	$ 18,185,000	$ (14,492,000)	$ 38,766,000
Allowance for Credit Losses, ACL [Member]
Financing Receivable [Abstract]
PCL	(3,991,000)	18,185,000	(14,492,000)	38,766,000
Allowance for Credit Losses, ACL [Member] | Other Construction [Member]
Financing Receivable [Abstract]
PCL	1,400,000
Allowance for Credit Losses, ACL [Member] | Secured by 1-4 Family Residential Properties [Member]
Financing Receivable [Abstract]
PCL	1,600,000
Allowance for Credit Losses, ACL [Member] | Commercial and Industrial Loans [Member]
Financing Receivable [Abstract]
PCL	(3,171,000)	(1,908,000)	880,000	(3,932,000)
Allowance for Credit Losses, ACL [Member] | State and Other Political Subdivision Loans [Member]
Financing Receivable [Abstract]
PCL	218,000	(27,000)	43,000	(1,270,000)
Allowance for Credit Losses, ACL [Member] | Other Commercial Loans [Member]
Financing Receivable [Abstract]
PCL	402,000	$ 307,000	(841,000)	$ (843,000)
Minimum [Member]
Financing Receivable [Abstract]
Credit amount used as baseline in evaluating loan policy	$ 100,000		$ 100,000