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 income	(347,334)						(439,883)	92,549
Stock issued for employee stock purchase plan	1,151		1		1,150
Stock-based compensation plans, net		$ 4,259		$ 2		$ 4,257
Stock issued for Spirit acquisition	464,918		183		464,735
Stock repurchases	(66,096)		(25)		(66,071)
Dividends on common stock	(45,844)							(45,844)
Balance at Jun. 30, 2022	3,259,895		1,288		2,569,060		(450,428)	1,139,975
Balance at Mar. 31, 2022	2,961,607		1,125		2,150,453		(326,961)	1,136,990
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	(96,013)						(123,467)	27,454
Stock-based compensation plans, net	3,893		0		3,893
Stock issued for Spirit acquisition		$ 464,918		$ 183		$ 464,735
Stock repurchases	(50,041)		(20)		(50,021)
Dividends on common stock	(24,469)							(24,469)
Balance at Jun. 30, 2022	3,259,895		1,288		2,569,060		(450,428)	1,139,975
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 income	151,475						47,572	103,903
Stock issued for employee stock purchase plan	833		0		833
Stock-based compensation plans, net	5,513		3		5,510
Stock repurchases	(20,022)		(11)		(20,011)
Dividends on common stock	(50,835)							(50,835)
Balance at Jun. 30, 2023	3,356,326		1,262		2,516,398		(469,988)	1,308,654
Balance at Mar. 31, 2023	3,339,901		1,273		2,533,589		(470,681)	1,275,720
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	59,007						693	58,314
Stock-based compensation plans, net	2,820		0		2,820
Stock repurchases	(20,022)		(11)		(20,011)
Dividends on common stock	(25,380)							(25,380)
Balance at Jun. 30, 2023	$ 3,356,326		$ 1,262		$ 2,516,398		$ (469,988)	$ 1,308,654