Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Spirit of Texas Bancshares, Inc.	Common Stock	Common Stock Spirit of Texas Bancshares, Inc.	Surplus	Surplus Spirit of Texas Bancshares, Inc.	Accumulated Other Comprehensive (Loss) Income	Undivided Profits
Balance at Dec. 31, 2021	$ 3,248,841		$ 1,127		$ 2,164,989		$ (10,545)	$ 1,093,270
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive (loss) income	(384,033)						(557,185)	173,152
Stock issued for employee stock purchase plan	1,151		1		1,150
Stock-based compensation plans, net	7,370		2		7,368
Stock issued for Spirit acquisition		$ 464,918		$ 183		$ 464,735
Stock repurchases	(111,133)		(44)		(111,089)
Dividends on common stock	(69,963)							(69,963)
Balance at Sep. 30, 2022	3,157,151		1,269		2,527,153		(567,730)	1,196,459
Balance at Jun. 30, 2022	3,259,895		1,288		2,569,060		(450,428)	1,139,975
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive (loss) income	(36,699)						(117,302)	80,603
Stock-based compensation plans, net	3,111				3,111
Stock repurchases	(45,037)		(19)		(45,018)
Dividends on common stock	(24,119)							(24,119)
Balance at Sep. 30, 2022	3,157,151		1,269		2,527,153		(567,730)	1,196,459
Balance at Dec. 31, 2022	3,269,362		1,270		2,530,066		(517,560)	1,255,586
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive (loss) income	124,330						(26,820)	151,150
Stock issued for employee stock purchase plan	833				833
Stock-based compensation plans, net	6,955		4		6,951
Stock repurchases	(39,999)		(23)		(39,976)
Dividends on common stock	(75,926)							(75,926)
Balance at Sep. 30, 2023	3,285,555		1,251		2,497,874		(544,380)	1,330,810
Balance at Jun. 30, 2023	3,356,326		1,262		2,516,398		(469,988)	1,308,654
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive (loss) income	(27,145)						(74,392)	47,247
Stock-based compensation plans, net	1,442		1		1,441
Stock repurchases	(19,977)		(12)		(19,965)
Dividends on common stock	(25,091)							(25,091)
Balance at Sep. 30, 2023	$ 3,285,555		$ 1,251		$ 2,497,874		$ (544,380)	$ 1,330,810