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Investment Securities - Additional Information (Detail)
 12 Months Ended
Dec. 31, 2023
USD ($)
security
Dec. 31, 2022
USD ($)
Dec. 31, 2021
USD ($)
Jun. 30, 2022
USD ($)
Apr. 01, 2022
USD ($)
Dec. 31, 2020
USD ($)
Schedule of Available-for-sale Securities [Line Items]            
Carrying value of investment securities $ 3,570,000,000 $ 2,350,000,000        
Investment securities pledged as collateral 142,100,000 131,100,000        
Available for sale securities sold 0 67,300,000 $ 17,900,000      
Realized gains (losses) on available for sale securities   0 $ 219,000      
Income tax expense benefit to net security gains and losses, percentage     25.74%      
Investment securities, provision for credit losses 1,700,000          
Investment securities, provision for credit losses 2,525,000 842,000 $ 842,000     $ 842,000
Allowance for credit loss, held-to-maturity 2,005,000 2,005,000 $ 0 $ 2,000,000   $ 0
Fair value of unrealized losses $ 333,485,000 $ 264,580,000        
Percentage of Company's investment portfolio 30.40% 33.00%        
Number of investment securities available for sale | security 1,583          
Number of investment in debt securities unrealized loss position | security 1,296          
Debt securities available for sale unrealized loss position $ 336,279,000 $ 407,967,000        
Number of investment securities held to maturity | security 507          
Number of investments in debt securities held-to-maturity unrealized loss position | security 486          
Unrealized losses $ 112,063,000 161,755,000        
Happy Bancshares, Inc.            
Schedule of Available-for-sale Securities [Line Items]            
Investment securities - available-for-sale, net of allowance for credit losses       $ 1,782,025,000 $ 1,773,540,000  
Investments reclassified from available-for-sale to held-to-maturity 1,120,000,000          
U.S. government-sponsored enterprises            
Schedule of Available-for-sale Securities [Line Items]            
Investment securities, provision for credit losses 0 0        
Allowance for credit loss, held-to-maturity 0 0        
Fair value of unrealized losses $ 17,091,000 20,153,000        
Number of investment in debt securities unrealized loss position | security 59          
Debt securities available for sale unrealized loss position $ 17,093,000 23,209,000        
Number of investments in debt securities held-to-maturity unrealized loss position | security 5          
Unrealized losses $ 2,607,000 3,349,000        
U.S. government-sponsored mortgage-backed securities            
Schedule of Available-for-sale Securities [Line Items]            
Investment securities, provision for credit losses 0 0        
Allowance for credit loss, held-to-maturity 0 0        
Fair value of unrealized losses $ 189,391,000 168,900,000        
Number of investment in debt securities unrealized loss position | security 669          
Debt securities available for sale unrealized loss position $ 191,557,000 215,405,000        
Number of investments in debt securities held-to-maturity unrealized loss position | security 18          
Unrealized losses $ 4,362,000 3,756,000        
Private mortgage-backed securities            
Schedule of Available-for-sale Securities [Line Items]            
Investment securities, provision for credit losses 0 0        
Fair value of unrealized losses $ 15,891,000 0        
Number of investment in debt securities unrealized loss position | security 32          
Debt securities available for sale unrealized loss position $ 16,117,000 18,302,000        
Non-government-sponsored asset backed securities            
Schedule of Available-for-sale Securities [Line Items]            
Investment securities, provision for credit losses 0 0        
Fair value of unrealized losses $ 7,551,000 4,928,000        
Number of investment in debt securities unrealized loss position | security 31          
Debt securities available for sale unrealized loss position $ 7,551,000 14,654,000        
State and political subdivisions            
Schedule of Available-for-sale Securities [Line Items]            
Investment securities, provision for credit losses 0 842,000        
Allowance for credit loss, held-to-maturity 2,005,000 2,005,000        
Fair value of unrealized losses $ 75,531,000 65,214,000        
Number of investment in debt securities unrealized loss position | security 444          
Debt securities available for sale unrealized loss position $ 75,931,000 115,698,000        
Number of investments in debt securities held-to-maturity unrealized loss position | security 463          
Unrealized losses $ 105,094,000 154,650,000        
Other securities            
Schedule of Available-for-sale Securities [Line Items]            
Investment securities, provision for credit losses 2,525,000 0        
Fair value of unrealized losses $ 28,030,000 5,385,000        
Number of investment in debt securities unrealized loss position | security 61          
Debt securities available for sale unrealized loss position $ 28,030,000 $ 20,699,000