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Derivative and Other Hedging Instruments (Fair Value Information) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative asset, fair value	$ 617	$ 317
Derivative liability, fair value	(99)	(86)
Derivative assets, at fair value	(617)	(317)
Derivative Liability	(99)	(86)
U.S. Treasury securities	353	471
U.S. Treasury Securities - short	(6,534)	(9,697)
Total - (short)/long, net	(6,181)	(9,226)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	4,679	1,054	$ (2,334)
Net Fair Value of Interest Rate Swaps Excluding the Recognition of Variation Margin Settlements as a Reduction of Carrying Value	4,500	1,600
TBA and Forward Settling Agency Securities [Member]
Derivative [Line Items]
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	312,307	352,658	286,586
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period		(356,349)	(263,544)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(2,860)	(552)	1,497
Interest Rate Swap [Member]
Derivative [Line Items]
Derivative Liability, Notional Amount	47,825	51,225
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	5,895	9,000	101,950
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	(9,295)	(1,000)	(137,800)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	4,400	1,117	(2,766)
Interest Rate Swap [Member] \| Fair Value, Inputs, Level 2 [Member]
Derivative [Line Items]
Derivative asset, fair value	2	0
Interest Rate Swaption [Member]
Derivative [Line Items]
Derivative Liability, Notional Amount	3,050	13,000
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	1,750	8,050	7,000
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	(11,700)	(5,450)	(5,450)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	857	23	(156)
Interest Rate Swaption [Member] \| Fair Value, Inputs, Level 2 [Member]
Derivative [Line Items]
Derivative asset, fair value	293	290
Purchases Of TBAs And Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative liability, fair value	(99)	(71)
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	(319,930)
US Treasury Securities [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	811	42	(106)
Credit Default Swap
Derivative [Line Items]
Derivative liability, fair value	0	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	56	0
Derivative Liability	0	(15)
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	(266)	(27)
Sale Of TBA And Forward Settling Agency Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Derivative [Line Items]
Derivative Liability	(99)	(71)
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	(266)
Short [Member] \| US Treasury Securities [Member]
Derivative [Line Items]
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	15,548	12,691	18,912
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	17,765	(14,388)	(16,849)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	1,482	444	(905)
Long [Member] \| US Treasury Securities [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(32)	(25)	102
Debt Securities, Trading, and Equity Securities, FV-NI	357	472	0	$ 95
Trading Securities Added During the Period	10,202	7,618	7,011
Notional Amount Of Trading Securities Settlement Expiration During The Period	$ (10,317)	$ (7,146)	$ (7,106)