Loans, Allowance for Credit Losses, and Asset Quality Information - Unfunded Loan Commitments (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended	9 Months Ended			12 Months Ended
	Jan. 01, 2023	Sep. 30, 2023	Sep. 30, 2022	Jun. 30, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2022
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 90,967	$ 109,230	$ 82,181	$ 90,967	$ 90,967	$ 78,789		$ 78,789
"Day 2" provision for credit losses on unfunded commitments acquired from GrandSouth		1,200	5,100		16,351	8,600		12,600
Charge-offs		(3,203)	(1,205)		(7,575)	(4,008)		(4,465)
Recoveries		971	511		2,845	3,206		4,043
Ending balance		108,198	86,587	109,230	108,198	86,587		90,967
Unfunded Loan Commitment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	13,306			13,306	13,306	13,506		13,506
"Day 2" provision for credit losses on unfunded commitments acquired from GrandSouth				(200)	(3,408)		$ (1,200)
Charge-offs				0	0		0
Recoveries				0	0		0
Ending balance		$ 11,819	$ 12,306		11,819	$ 12,306		$ 13,306
Unfunded Loan Commitment | GrandSouth
Financing Receivable, Allowance for Credit Loss [Roll Forward]
"Day 2" provision for credit losses on unfunded commitments acquired from GrandSouth	$ 1,900			$ 0	$ 1,921		$ 0