Goodwill and Other Intangible Assets - Changes in Goodwill and Other Intangibles (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Finite-lived Intangible Assets [Roll Forward]
Core deposit premiums, beginning of period			$ 128,951
Amortization	$ (4,097)	$ (4,225)	(12,291)	$ (11,807)
Core deposit premiums, end of period	116,660		116,660		$ 128,951
Spirit of Texas Bancshares, Inc.
Finite-lived Intangible Assets [Roll Forward]
Core deposit premiums, beginning of period			36,500
Core deposit premiums, end of period					36,500
Core Deposit Premium
Finite-lived Intangible Assets [Roll Forward]
Core deposit premiums, beginning of period			116,016	93,862	93,862
Acquisitions			0		36,500
Amortization			(11,066)		(14,346)
Core deposit premiums, end of period	104,950		104,950		116,016
Books of Business Intangible
Finite-lived Intangible Assets [Roll Forward]
Core deposit premiums, beginning of period			12,935	$ 12,373	12,373
Acquisitions			0		2,131
Amortization			(1,225)		(1,569)
Core deposit premiums, end of period	$ 11,710		$ 11,710		$ 12,935