v3.22.4
Securities (Securities Moody's and Standard & Poor's Bond Rating) (Details) - USD ($)
$ in Thousands
Dec. 31, 2022
Dec. 31, 2021
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost $ 2,639,241 $ 1,749,337
States and Political Subdivisions [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost 2,111,619 1,220,573
States and Political Subdivisions [Member] | Not Guaranteed or Pre-Refunded [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost 567,216  
States and Political Subdivisions [Member] | Guaranteed by the Texas PSF [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost 1,422,442  
States and Political Subdivisions [Member] | Pre-Refunded [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost 121,961  
Other [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost 1,500 $ 1,500
Aaa/AAA [Member] | States and Political Subdivisions [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost 1,817,604  
Aaa/AAA [Member] | States and Political Subdivisions [Member] | Not Guaranteed or Pre-Refunded [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost 273,201  
Aaa/AAA [Member] | States and Political Subdivisions [Member] | Guaranteed by the Texas PSF [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost 1,422,442  
Aaa/AAA [Member] | States and Political Subdivisions [Member] | Pre-Refunded [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost 121,961  
Aaa/AAA [Member] | Other [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost 0  
Aa/AA [Member] | States and Political Subdivisions [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost 294,015  
Aa/AA [Member] | States and Political Subdivisions [Member] | Not Guaranteed or Pre-Refunded [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost 294,015  
Aa/AA [Member] | States and Political Subdivisions [Member] | Guaranteed by the Texas PSF [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost 0  
Aa/AA [Member] | States and Political Subdivisions [Member] | Pre-Refunded [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost 0  
Aa/AA [Member] | Other [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost 0  
Not rated [Member] | States and Political Subdivisions [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost 0  
Not rated [Member] | States and Political Subdivisions [Member] | Not Guaranteed or Pre-Refunded [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost 0  
Not rated [Member] | States and Political Subdivisions [Member] | Guaranteed by the Texas PSF [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost 0  
Not rated [Member] | States and Political Subdivisions [Member] | Pre-Refunded [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost 0  
Not rated [Member] | Other [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held to Maturity, Amortized Cost $ 1,500