Derivative and Other Hedging Instruments (Effect Of Derivative Instruments Not Designated As Hedges On Comprehensive Income Statement) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Amount Gain/(Loss) Recognized in Income on Derivatives	$ 4,679	$ 1,054	$ (2,334)
Interest Rate Swaption [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	(3,050)	(13,000)	(10,400)
Additions	(1,750)	(8,050)	(7,000)
Settlement, Expirations or Exercise	11,700	5,450	5,450
Notional Amount	(3,050)	(13,000)
Amount Gain/(Loss) Recognized in Income on Derivatives	857	23	(156)
TBA and Forward Settling Agency Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	(19,050)	(26,673)	(30,364)	$ (7,322)
Additions	(312,307)	(352,658)	(286,586)
Settlement, Expirations or Exercise		356,349	263,544
Amount Gain/(Loss) Recognized in Income on Derivatives	(2,860)	(552)	1,497
Purchases Of TBAs And Forward Settling Agency Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Settlement, Expirations or Exercise	319,930
Interest Rate Swap [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Additions	(5,895)	(9,000)	(101,950)
Settlement, Expirations or Exercise	9,295	1,000	137,800
Notional Amount	(47,825)	(51,225)
Amount Gain/(Loss) Recognized in Income on Derivatives	4,400	1,117	(2,766)
US Treasury Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Amount Gain/(Loss) Recognized in Income on Derivatives	811	42	(106)
Receiver Swaption [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	0	0
Additions	(150)
Settlement, Expirations or Exercise	(150)
Amount Gain/(Loss) Recognized in Income on Derivatives	0
Forward Settling non-Agency Securities
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	0	(450)	0
Additions	0	(1,800)
Amount Gain/(Loss) Recognized in Income on Derivatives	0	5
Purchases Of Forward Settling non-Agency Securities
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Settlement, Expirations or Exercise	450	1,350
Credit Default Swap, Buying Protection
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	(215)
Additions	5,835
Settlement, Expirations or Exercise	(5,620)
Amount Gain/(Loss) Recognized in Income on Derivatives	21
Not Designated as Hedging Instrument [Member] | Interest Rate Swaption [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount			(10,400)	(8,850)
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	(47,825)	(51,225)	(43,225)	(79,075)
Not Designated as Hedging Instrument [Member] | Credit Default Swap, Buying Protection
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	(215)	0
Short [Member] | US Treasury Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	(7,373)	(9,590)	(11,287)	(9,224)
Additions	(15,548)	(12,691)	(18,912)
Settlement, Expirations or Exercise	(17,765)	14,388	16,849
Amount Gain/(Loss) Recognized in Income on Derivatives	1,482	444	(905)
Long [Member] | US Treasury Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Amount Gain/(Loss) Recognized in Income on Derivatives	(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)
Future [Member] | Short [Member] | US Treasury Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	(9,213)	(1,500)	(1,000)	$ (1,000)
Additions	37,493	(6,000)	(4,000)
Settlement, Expirations or Exercise	$ (29,780)	$ 5,500	$ 4,000