v3.26.1
Derivative and Other Hedging Instruments (Fair Value Information) (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 [Line Items]                
Derivative asset, fair value $ 260   $ 260     $ 169    
Derivative liability, fair value (137)   (137)     (6)    
Derivative assets, at fair value 260   260     169    
Derivative Liability (137)   (137)     (6)    
U.S. Treasury securities 12,325   12,325     13,477    
U.S. Treasury Securities - short (18,150)   (18,150)     (16,452)    
Total - (short)/long, net (5,825)   (5,825)     (2,975)    
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net 487 $ (369) 869 $ (1,380)        
Net Fair Value of Interest Rate Swaps Excluding the Recognition of Variation Margin Settlements as a Reduction of Carrying Value 2,200   2,200     1,300    
TBA and Forward Settling Agency Securities [Member]                
Derivative [Line Items]                
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 Instruments Not Designated as Hedging Instruments, Gain (Loss), Net (36) 11 (90) 88        
Derivative, Fair Value, Net 52   52     71    
Interest Rate Swap [Member]                
Derivative [Line Items]                
Derivative Liability, Notional Amount 73,752   73,752     64,632    
Derivative liability, fair value 0   0     0    
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period 400 2,600 51,020 10,750        
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period (3,150) (5,300) (41,900) (5,300)        
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net 640 (236) 1,095 (805)        
Interest Rate Swap [Member] | Fair Value, Inputs, Level 2 [Member]                
Derivative [Line Items]                
Derivative asset, fair value 111   111     57    
Interest Rate Swaption [Member]                
Derivative [Line Items]                
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 Instruments Not Designated as Hedging Instruments, Gain (Loss), Net   (9)   (28)        
Interest Rate Swaption [Member] | Fair Value, Inputs, Level 2 [Member]                
Derivative [Line Items]                
Derivative asset, fair value 31   31     24    
Purchases Of TBAs And Forward Settling Agency Securities [Member]                
Derivative [Line Items]                
Derivative liability, fair value (24)   (24)     (6)    
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period (52,510) (35,103) (108,198)          
SOFR Futures Contracts                
Derivative [Line Items]                
Derivative liability, fair value (4)   (4)     0    
US Treasury Securities [Member] | Fair Value, Recurring [Member] | Future [Member] | Fair Value, Inputs, Level 1 [Member]                
Derivative [Line Items]                
Derivative assets, at fair value (42)   (42)     (11)    
Derivative Liability 109   109     0    
TBA and Forward Settling Agency Securities [Member] | Fair Value, Recurring [Member] | Purchases Of TBAs And Forward Settling Agency Securities [Member] | Fair Value, Inputs, Level 2 [Member]                
Derivative [Line Items]                
Derivative assets, at fair value 76   76     77    
Sale Of TBA And Forward Settling Agency Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]                
Derivative [Line Items]                
Derivative Liability (24)   (24)     (6)    
Sale Of TBA And Forward Settling Agency Securities [Member] | Fair Value, Recurring [Member] | Purchases Of TBAs And Forward Settling Agency Securities [Member] | Fair Value, Inputs, Level 2 [Member]                
Derivative [Line Items]                
Derivative assets, at fair value 76   76          
Short [Member] | US Treasury Securities [Member]                
Derivative [Line Items]                
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 Instruments Not Designated as Hedging Instruments, Gain (Loss), Net 81 (139) 259 (599)        
Short [Member] | US Treasury Securities [Member] | Future [Member]                
Derivative [Line Items]                
Derivative assets, at fair value 0   0     (8)    
Derivative Liability (108)   (108)     0    
Long [Member] | US Treasury Securities [Member]                
Derivative [Line Items]                
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net (67) 0 (134) 60        
Debt Securities, Trading, and Equity Securities, FV-NI 12,500 3,545 12,500 3,545 $ 12,686 13,458 $ 3,216 $ 1,585
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)        
Long [Member] | SOFR Futures Contracts                
Derivative [Line Items]                
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net   $ 3 (4) $ 13        
Long [Member] | US Treasury Securities [Member] | Future [Member]                
Derivative [Line Items]                
Derivative assets, at fair value (42)   (42)     (3)    
Derivative Liability $ (1)   $ (1)     $ 0