v3.26.1
Available for Sale Securities (Details)
3 Months Ended
Mar. 31, 2026
USD ($)
Mar. 31, 2025
USD ($)
Dec. 31, 2025
USD ($)
Debt Securities, Available-for-sale [Line Items]      
Available-for-sale Securities, Amortized Cost $ 13,756,543,000   $ 13,739,191,000
Available-for-sale Securities, Fair Value 13,539,565,000   13,606,625,000
Available-for-sale Securities, Gross Unrealized Gain 82,878,000   141,234,000
Available-for-sale Securities, Gross Unrealized Loss (299,856,000)   (273,800,000)
Debt Securities, Available-for-sale, Maturity, Fair Value, Rolling Maturity [Abstract]      
Proceeds from sales of available-for-sale securities 0 $ 0  
Asset Pledged as Collateral with Right      
Debt Securities, Available-for-sale, Maturity, Fair Value, Rolling Maturity [Abstract]      
Pledged Securities 11,700,000,000   11,500,000,000
Fixed Maturity Securities [Member]      
Debt Securities, Available-for-sale, Maturity, Amortized Cost, Rolling Maturity [Abstract]      
Available-for-sale Securities, Debt Maturities, Less than One Year, Amortized Cost Basis 411,265,000    
Available-for-sale Securities, Debt Maturities, One to Five Years, Amortized Cost Basis 2,127,784,000    
Available-for-sale Securities, Debt Maturities, Six To Ten Years, Amortized Cost Basis 316,397,000    
Available-for-sale Securities, Debt Maturities, Over Ten Years, Amortized Cost Basis 454,432,000    
Available-for-sale Securities, Debt Maturities, Allocated and Single Maturity Date, Amortized Cost 3,309,878,000    
Debt Securities, Available-for-sale, Maturity, Fair Value, Rolling Maturity [Abstract]      
Available-for-sale Securities, Debt Maturities, Less than One Year, Fair Value 406,840,000    
Available-for-sale Securities, Debt Maturities, One to Five Years, Fair Value 2,030,088,000    
Available-for-sale Securities, Debt Maturities, Six to Ten Years, Fair Value 305,609,000    
Available-for-sale Securities, Debt Maturities, Over Ten Years, Fair Value 448,238,000    
Available-for-sale Securities, Debt Maturities, Allocated and Single Maturity Date, Fair Value $ 3,190,775,000    
Available-for-sale Securities, Debt Maturities, Weighted Average Maturity [1] 4.82    
U.S. Treasury [Member]      
Debt Securities, Available-for-sale [Line Items]      
Available-for-sale Securities, Amortized Cost $ 1,000,000   1,001,000
Available-for-sale Securities, Fair Value 984,000   980,000
Available-for-sale Securities, Gross Unrealized Gain 0   0
Available-for-sale Securities, Gross Unrealized Loss (16,000)   (21,000)
Municipal securities [Member]      
Debt Securities, Available-for-sale [Line Items]      
Available-for-sale Securities, Amortized Cost 181,371,000   190,917,000
Available-for-sale Securities, Fair Value 175,123,000   184,273,000
Available-for-sale Securities, Gross Unrealized Gain 0   0
Available-for-sale Securities, Gross Unrealized Loss (6,248,000)   (6,644,000)
Commercial agency mortgage-backed securities [Member]      
Debt Securities, Available-for-sale [Line Items]      
Available-for-sale Securities, Amortized Cost 3,127,007,000   3,240,728,000
Available-for-sale Securities, Fair Value 3,014,195,000   3,126,244,000
Available-for-sale Securities, Gross Unrealized Gain 5,346,000   7,622,000
Available-for-sale Securities, Gross Unrealized Loss (118,158,000)   (122,106,000)
Other debt securities [Member]      
Debt Securities, Available-for-sale [Line Items]      
Available-for-sale Securities, Amortized Cost 500,000   500,000
Available-for-sale Securities, Fair Value 473,000   473,000
Available-for-sale Securities, Gross Unrealized Gain 0   0
Available-for-sale Securities, Gross Unrealized Loss (27,000)   (27,000)
Residential Mortgage Backed Securities [Member]      
Debt Securities, Available-for-sale, Maturity, Amortized Cost, Rolling Maturity [Abstract]      
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost [2] 10,446,665,000    
Debt Securities, Available-for-sale, Maturity, Fair Value, Rolling Maturity [Abstract]      
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value $ 10,348,790,000    
Available-for-sale Securities, Debt Maturities, Average Expected Life of Mortgage-backed Securities 4 years 2 months 12 days    
Residential agency mortgage-backed securities [Member]      
Debt Securities, Available-for-sale [Line Items]      
Available-for-sale Securities, Amortized Cost $ 9,710,464,000   9,593,919,000
Available-for-sale Securities, Fair Value 9,631,722,000   9,598,627,000
Available-for-sale Securities, Gross Unrealized Gain 67,045,000   121,838,000
Available-for-sale Securities, Gross Unrealized Loss (145,787,000)   (117,130,000)
Residential non-agency mortgage-backed securities [Member]      
Debt Securities, Available-for-sale [Line Items]      
Available-for-sale Securities, Amortized Cost 736,201,000   712,126,000
Available-for-sale Securities, Fair Value 717,068,000   696,028,000
Available-for-sale Securities, Gross Unrealized Gain 10,487,000   11,774,000
Available-for-sale Securities, Gross Unrealized Loss $ (29,620,000)   $ (27,872,000)
[1] Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without penalty.
[2] The average expected lives of residential mortgage-backed securities were 4.2 years based upon current prepayment assumptions.