Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Preferred Stock	Common Stock	Surplus	Accumulated Other Comprehensive Income (Loss)	Undivided Profits	Undivided Profits Cumulative Effect, Period of Adoption, Adjustment	Reliance Bancshares, Inc.	Reliance Bancshares, Inc. Preferred Stock	Reliance Bancshares, Inc. Common Stock	Reliance Bancshares, Inc. Surplus	Landrum Company	Landrum Company Preferred Stock	Landrum Company Common Stock	Landrum Company Surplus	Landmark Bank	Landmark Bank Common Stock	Landmark Bank Surplus	Triumph	Triumph Common Stock	Triumph Surplus
Balance at Dec. 31, 2018	$ 2,246,434		$ 0	$ 923	$ 1,597,944	$ (27,374)	$ 674,941
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	286,432					48,265	238,167
Stock issued for employee stock purchase plan	1,312			1	1,311
Stock-based compensation plans, net	10,532			3	10,529
Stock issued for acquisition									$ 144,830	$ 42,000	$ 40	$ 102,790	$ 415,772	$ 767	$ 173	$ 414,832
Preferred stock retirement	(42,000)		(42,000)
Stock repurchases	(10,128)			(4)	(10,124)
Dividends on preferred stock	(339)						(339)
Dividends on common stock	(63,921)						(63,921)
Balance at Dec. 31, 2019	$ 2,988,924	$ (128,101)	767	1,136	2,117,282	20,891	848,848	$ (128,101)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-13 [Member]
Comprehensive income	$ 293,739					38,835	254,904
Stock issued for employee stock purchase plan	956			1	955
Stock-based compensation plans, net	9,110			3	9,107
Stock repurchases	(113,327)			(59)	(113,268)
Dividends on preferred stock	(52)						(52)
Dividends on common stock	(74,593)						(74,593)
Balance at Dec. 31, 2020	2,976,656		767	1,081	2,014,076	59,726	901,006
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	200,885					(70,271)	271,156
Stock issued for employee stock purchase plan	1,170			1	1,169
Stock-based compensation plans, net	16,158			4	16,154
Stock issued for acquisition																	$ 138,191	$ 45	$ 138,146	$ 127,899	$ 42	$ 127,857
Preferred stock retirement	(767)		(767)
Stock repurchases	(132,459)			(46)	(132,413)
Dividends on preferred stock	(47)						(47)
Dividends on common stock	(78,845)						(78,845)
Balance at Dec. 31, 2021	$ 3,248,841		$ 0	$ 1,127	$ 2,164,989	$ (10,545)	$ 1,093,270