Investment Securities (Summary Of Amount Of Gross Unrealized Losses For Debt Securities And Estimated Fair Value) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Investment [Line Items]
Available-for-sale, Less than 12 months - Gross unrealized losses	$ 39	$ 44
Available-for-sale, Less than 12 months - Estimated fair value	2,772	5,379
Available-for-sale, 12 months or more - Gross unrealized losses	287	137
Available-for-sale, 12 months or more - Estimated fair value	8,937	6,422
Available-for-sale, Total - Gross unrealized losses	326	181
Available-for-sale, Total - Estimated fair value	11,709	11,801
Investment Securities Gross Unrealized Losses Less Than 12 Months	40	47
Investment Securities Estimated Fair Value Less Than 12 Months	2,858	5,642
Investment Securities Gross Unrealized Losses 12 Months or More	297	147
Investment Securities Estimated Fair Value 12 Months or More	9,375	6,714
Investment Securities Gross Unrealized Losses Total	337	194
Investment Securities Estimated Fair Value Total	12,233	12,356
US States and Political Subdivisions Debt Securities [Member]
Investment [Line Items]
Held-to-maturity, Less than 12 months - Gross unrealized losses	1	3
Held-to-maturity, Less than 12 months - Estimated fair value	86	263
Held-to-maturity, 12 months or more - Gross unrealized losses	10	10
Held-to-maturity, 12 months or more - Estimated fair value	438	292
Held-to-maturity, Total - Gross unrealized losses	11	13
Held-to-maturity, Total - Estimated fair value	524	555
Available-for-sale, Less than 12 months - Gross unrealized losses	2	6
Available-for-sale, Less than 12 months - Estimated fair value	266	554
Available-for-sale, 12 months or more - Gross unrealized losses	14	5
Available-for-sale, 12 months or more - Estimated fair value	641	230
Available-for-sale, Total - Gross unrealized losses	16	11
Available-for-sale, Total - Estimated fair value	907	784
Available-for-sale, Unrealized losses, Other [Member]
Investment [Line Items]
Available-for-sale, Less than 12 months - Gross unrealized losses	0	0
Available-for-sale, Less than 12 months - Estimated fair value	0	0
Available-for-sale, 12 months or more - Gross unrealized losses	4	1
Available-for-sale, 12 months or more - Estimated fair value	11	14
Available-for-sale, Total - Gross unrealized losses	4	1
Available-for-sale, Total - Estimated fair value	11	14
Agency Securities [Member]
Investment [Line Items]
Available-for-sale, Less than 12 months - Gross unrealized losses	2	6
Available-for-sale, Less than 12 months - Estimated fair value	245	808
Available-for-sale, 12 months or more - Gross unrealized losses	17	7
Available-for-sale, 12 months or more - Estimated fair value	913	808
Available-for-sale, Total - Gross unrealized losses	19	13
Available-for-sale, Total - Estimated fair value	1,158	1,616
Agency Guaranteed Mortgage Backed Securities [Member]
Investment [Line Items]
Available-for-sale, Less than 12 months - Gross unrealized losses	16	29
Available-for-sale, Less than 12 months - Estimated fair value	1,081	3,609
Available-for-sale, 12 months or more - Gross unrealized losses	224	112
Available-for-sale, 12 months or more - Estimated fair value	6,661	4,721
Available-for-sale, Total - Gross unrealized losses	240	141
Available-for-sale, Total - Estimated fair value	7,742	8,330
Small Business Administration Loan Backed Securities [Member]
Investment [Line Items]
Available-for-sale, Less than 12 months - Gross unrealized losses	19	3
Available-for-sale, Less than 12 months - Estimated fair value	1,180	408
Available-for-sale, 12 months or more - Gross unrealized losses	28	12
Available-for-sale, 12 months or more - Estimated fair value	711	649
Available-for-sale, Total - Gross unrealized losses	47	15
Available-for-sale, Total - Estimated fair value	$ 1,891	$ 1,057