Investment Securities (Summary Of Net Gain From Sale Of Agency Securities) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Cost of Sale of Fair Value Option Securities	$ (4,472)	$ (7,769)	$ (53,912)	$ (12,331)
Cost of Sale of Investment Securities	(5,750)	(8,135)	(55,345)	(13,036)
Proceeds from agency MBS sold			16,206	7,122
Net gain (loss) on sale of investment securities	153	132	647	192
Available-for-sale Securities [Member]
Agency MBS sold, at cost	(1,278)	(366)	(1,433)	(705)
Proceeds from agency MBS sold	1,317	361	1,473	696
Net gain (loss) on sale of investment securities		(5)		(9)
Gross gain on sale of investment securities	39	0	40	0
Gross loss on sale of investment securities	0	(5)	0	(9)
Securities Remeasured at Fair Value [Member]
Proceeds from agency MBS sold	4,586	7,906	54,519	12,532
Net gain (loss) on sale of investment securities		137		201
Gross gain on sale of investment securities	129	138	696	204
Gross loss on sale of investment securities	(15)	(1)	(89)	(3)
Securities (Assets) [Member]
Proceeds from agency MBS sold	5,903	8,267	55,992	13,228
Net gain (loss) on sale of investment securities	153	132	647	192
Gross gain on sale of investment securities	168	138	736	204
Gross loss on sale of investment securities	(15)	$ (6)	(89)	$ (12)
Cost and Proceeds of Investment Securities [Member] | Available-for-sale Securities [Member]
Net gain (loss) on sale of investment securities	39		40
Cost and Proceeds of Investment Securities [Member] | Securities Remeasured at Fair Value [Member]
Net gain (loss) on sale of investment securities	114		607
Gross Gain & Loss of Investment Securities [Member] | Available-for-sale Securities [Member]
Net gain (loss) on sale of investment securities	39		40
Gross Gain & Loss of Investment Securities [Member] | Securities Remeasured at Fair Value [Member]
Net gain (loss) on sale of investment securities	$ 114		$ 607