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Investment Securities - Schedule of Amortized Cost and Estimated Fair Value of Investments Available-for-Sale by Contractual Maturity (Details) - USD ($)
$ in Thousands
Mar. 31, 2024
Dec. 31, 2023
Amortized Cost    
Total investment securities available-for-sale $ 1,613,659 $ 1,668,316
Estimated Fair Value    
Less: allowance for credit losses (17) (17)
Total investment securities available-for-sale 1,445,034  
Amortized Cost    
Less: allowance for credit losses 1,957 1,956
Total held-to-maturity securities, net of ACL 1,000,732 1,015,737
Estimated Fair Value    
Total investment securities held-to-maturity 878,159 901,582
Asset-Backed Securities    
Amortized Cost    
Within one year 139,224  
One to five years 486,394  
Five to ten years 112,838  
Beyond ten years 20,392  
Estimated Fair Value    
Within one year 135,426  
One to five years 446,955  
Five to ten years 97,570  
Beyond ten years 17,612  
Amortized Cost    
Within one year 4,282  
One to five years 61,707  
Five to ten years 117,237  
Beyond ten years 74,109  
Less: allowance for credit losses 1,957  
Total held-to-maturity securities, net of ACL 1,000,732  
Total 2,614,391  
Estimated Fair Value    
Within one year 4,247  
One to five years 59,309  
Five to ten years 102,274  
Beyond ten years 67,323  
Total investment securities held-to-maturity 878,159  
Total 2,323,193  
Residential mortgage-backed securities    
Amortized Cost    
Amortized cost, without maturity date 800,793  
Total investment securities available-for-sale 800,793 823,992
Estimated Fair Value    
Estimated fair value, without maturity date 698,550  
Less: allowance for credit losses 0 0
Amortized Cost    
Amortized cost, without maturity date 655,388  
Estimated Fair Value    
Estimated fair value, without maturity date 568,040  
Total investment securities held-to-maturity 568,040 590,063
Commercial mortgage-backed securities    
Amortized Cost    
Amortized cost, without maturity date 54,018  
Total investment securities available-for-sale 54,018 54,557
Estimated Fair Value    
Estimated fair value, without maturity date 48,938  
Less: allowance for credit losses 0 0
Amortized Cost    
Amortized cost, without maturity date 89,966  
Estimated Fair Value    
Estimated fair value, without maturity date 76,966  
Total investment securities held-to-maturity $ 76,966 $ 77,360