Investment Securities (Summary Of Net Gain From Sale Of Agency Securities) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Proceeds from agency MBS sold			$ 2,947	$ 30,854
Net gain (loss) on sale of MBS	$ 55	$ (22)	53	14
Available-for-sale Securities [Member]
Agency MBS sold, at cost	(7,508)	(10,241)	(11,023)	(17,974)
Proceeds from agency MBS sold	7,563	10,219	11,076	17,988
Net gain (loss) on sale of MBS	55	(22)	53	14
Gross gain on sale of MBS	55	22	60	79
Gross loss on sale of MBS	0	(44)	(7)	(65)
Interest Only And Principal Only Strip [Member]
Unrealized Gain (Loss) on Securities	$ 0	$ (7)	$ 11	$ 4