v3.26.1
Derivative and Other Hedging Instruments (Narrative) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Mar. 31, 2026
Dec. 31, 2025
Mar. 31, 2025
Dec. 31, 2024
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net $ 487 $ (369) $ 869 $ (1,380)        
Derivative assets, at fair value 260   260     $ 169    
Derivative liability, fair value (137)   (137)     (6)    
Interest Rate Swaption [Member]                
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net   (9)   (28)        
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period   0   1,500        
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period   0   (1,500)        
Derivative, Notional Amount   2,000   2,000     $ 2,000  
TBA and Forward Settling Agency Securities [Member]                
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net (36) 11 (90) 88        
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period 51,648 35,699 105,065 63,666        
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period       (62,214)        
Derivative Asset, Fair Value, Gross Asset 9,728   9,728     12,988    
Derivative, Fair Value, Net 52   52     71    
Derivative, Notional Amount 10,047 8,407 10,047 8,407 $ 10,909 13,180 7,811 $ 6,955
SOFR Futures Contracts                
Derivative, Notional Amount 2,600 1,200 2,600 1,200        
Derivative liability, fair value (4)   (4)     0    
Not Designated as Hedging Instrument [Member] | Interest Rate Swaption [Member]                
Derivative, Notional Amount               2,000
Short [Member] | US Treasury Securities [Member]                
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net 81 (139) 259 (599)        
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period 5,340 7,971 10,339 11,792        
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period (4,132) (4,211) (8,347) (8,188)        
Derivative, Notional Amount 18,370 21,396 18,370 21,396 17,162 16,378 17,636 17,792
Long [Member] | US Treasury Securities [Member]                
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net (67) 0 (134) 60        
Trading Securities Added During the Period 757 3,968 25,807 9,356        
Notional Amount Of Trading Securities Settlement Expiration During The Period (943) (3,639) (26,765) (7,396)        
Debt Securities, Trading, and Equity Securities, FV-NI $ 12,500 3,545 12,500 3,545 $ 12,686 $ 13,458 $ 3,216 $ 1,585
Long [Member] | SOFR Futures Contracts                
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net   $ 3 $ (4) $ 13