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Investments - Narrative (Details)
 12 Months Ended
Dec. 31, 2024
USD ($)
security
Dec. 31, 2023
USD ($)
security
Dec. 31, 2022
USD ($)
Debt Securities, Available-for-sale [Line Items]      
Amortized cost $ 2,025,483,000 $ 1,769,134,000  
Other Investments and Securities, at Cost $ 72,784,000 $ 66,195,000  
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | security 830 753  
Gross Unrealized Gains $ 1,187,000 $ 1,603,000  
Maximum percentage of shareholders' equity security holdings held of one issuer 10.00% 10.00%  
Available-for-sale securities pledged as collateral, fair value $ 1,500,000,000 $ 1,600,000,000  
Weighted average life (in years) 5 years    
ACL on held-to-maturity securities $ 257,000 785,000  
Proceeds from Sale of Debt Securities, Available-for-Sale 0 40,393,000 $ 0
Gross gains realized 0 601,000 $ 0
Provisions For Credit Losses, Available-For-Sale 4,200,000    
Debt Securities, Provision For Credit Losses, Chargeoff 4,200,000    
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Excluding Accrued Interest 0 0  
Accrued interest receivable, held-to-maturity securities 8,600,000 6,500,000  
Des Moines      
Debt Securities, Available-for-sale [Line Items]      
Other Investments and Securities, at Cost 8,700,000 7,800,000  
Reclassified to Held to Maturity [Member]      
Debt Securities, Available-for-sale [Line Items]      
Gross Unrealized Gains $ 10,800,000 14,100,000  
Debt Securities, Available-for-sale, Amortized Cost   $ 0