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Derivatives (Narrative) (Details)
12 Months Ended
Dec. 31, 2025
USD ($)
SwapAgreements
Dec. 31, 2024
USD ($)
Dec. 31, 2023
USD ($)
Derivative [Line Items]      
Notional amount of derivatives $ 8,040,346,000 $ 7,392,532,000  
Payments for (Proceeds from) Hedge, Investing Activities, Total (2,270,000) 13,730,000 $ (16,360,000)
Fair value liability 1,300,000 2,100,000  
Credit risk-related contingent features, net liability position 13,200,000 39,100,000  
Credit risk-related contingent features, posted collateral 13,000,000 38,000,000  
Derivatives Designated as Hedging Instruments [Member]      
Derivative [Line Items]      
Notional amount of derivatives $ 2,172,500,000 1,827,500,000  
Interest Rate Swaps [Member] | Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedge [Member]      
Derivative [Line Items]      
Amortization of accumulated other comprehensive loss on terminated cash flow hedges   $ 13,700,000 2,900,000
Number of terminated interest rate swap agreements | SwapAgreements 0    
Derivative Maturity Year 2029    
Derivative maturity expiration year 2029    
Interest Rate Swaps [Member] | Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedge [Member] | Swap Agreement 3, Expires 2025 [Member]      
Derivative [Line Items]      
Notional amount of derivatives $ 425,000,000    
Derivative Maturity Year 2026    
Derivative maturity expiration year 2026    
Interest Rate Swaps [Member] | Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedge [Member] | Swap Agreement 4, Expires 2026 [Member]      
Derivative [Line Items]      
Notional amount of derivatives $ 825,000,000    
Derivative Maturity Year 2027    
Derivative maturity expiration year 2027    
Interest Rate Swaps [Member] | Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedge [Member] | Swap Agreement 5, Expires 2027 [Member]      
Derivative [Line Items]      
Notional amount of derivatives $ 50,000,000    
Derivative Maturity Year   2028  
Derivative maturity expiration year   2028  
Interest Rate Swaps [Member] | Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedge [Member] | Swap Agreement 6, Expires Thereafter [Member]      
Derivative [Line Items]      
Notional amount of derivatives 275,000,000    
Interest Rate Swaps [Member] | Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedge [Member] | Swap Agreement 7, Expires 2030 [Member]      
Derivative [Line Items]      
Notional amount of derivatives $ 200,000,000    
Derivative Maturity Year 2030    
Derivative maturity expiration year 2030    
Interest Rate Swaps [Member] | Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedging [Member]      
Derivative [Line Items]      
Payments for (Proceeds from) Hedge, Investing Activities, Total $ 2,300   $ 19,300
Interest Rate Swaps - Securities [Member] | Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedging [Member]      
Derivative [Line Items]      
Notional amount of derivatives 397,500,000 $ 477,500,000  
Derivative hedged item   $ 373,800,000  
Basis adjustment associated with hedged items loss 23,700,000    
Interest Rate Swaps - Securities [Member] | Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedging [Member] | Commercial Mortgage-Backed Securities [Member]      
Derivative [Line Items]      
Amortized cost basis of closed portfolio of pre-payable securities $ 432,000,000