Investment Securities (Summary Of Amount Of Gross Unrealized Losses For Debt Securities And Estimated Fair Value) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Investment [Line Items]
Available-for-sale, Less than 12 months - Gross unrealized losses	$ 7	$ 39
Available-for-sale, Less than 12 months - Estimated fair value	1,617	2,772
Available-for-sale, 12 months or more - Gross unrealized losses	80	287
Available-for-sale, 12 months or more - Estimated fair value	4,794	8,937
Available-for-sale, Total - Gross unrealized losses	87	326
Available-for-sale, Total - Estimated fair value	6,411	11,709
Investment Securities Gross Unrealized Losses Less Than 12 Months	7	40
Investment Securities Estimated Fair Value Less Than 12 Months	1,690	2,858
Investment Securities Gross Unrealized Losses 12 Months or More	80	297
Investment Securities Estimated Fair Value 12 Months or More	4,839	9,375
Investment Securities Gross Unrealized Losses Total	87	337
Investment Securities Estimated Fair Value Total	6,529	12,233
US States and Political Subdivisions Debt Securities [Member]
Investment [Line Items]
Held-to-maturity, Less than 12 months - Gross unrealized losses	0	1
Held-to-maturity, Less than 12 months - Estimated fair value	73	86
Held-to-maturity, 12 months or more - Gross unrealized losses	0	10
Held-to-maturity, 12 months or more - Estimated fair value	45	438
Held-to-maturity, Total - Gross unrealized losses	0	11
Held-to-maturity, Total - Estimated fair value	118	524
Available-for-sale, Less than 12 months - Gross unrealized losses	0	2
Available-for-sale, Less than 12 months - Estimated fair value	50	266
Available-for-sale, 12 months or more - Gross unrealized losses	0	14
Available-for-sale, 12 months or more - Estimated fair value	5	641
Available-for-sale, Total - Gross unrealized losses	0	16
Available-for-sale, Total - Estimated fair value	55	907
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	0	4
Available-for-sale, 12 months or more - Estimated fair value	0	11
Available-for-sale, Total - Gross unrealized losses	0	4
Available-for-sale, Total - Estimated fair value	0	11
Agency Securities [Member]
Investment [Line Items]
Available-for-sale, Less than 12 months - Gross unrealized losses	2	2
Available-for-sale, Less than 12 months - Estimated fair value	222	245
Available-for-sale, 12 months or more - Gross unrealized losses	2	17
Available-for-sale, 12 months or more - Estimated fair value	359	913
Available-for-sale, Total - Gross unrealized losses	4	19
Available-for-sale, Total - Estimated fair value	581	1,158
Agency Guaranteed Mortgage Backed Securities [Member]
Investment [Line Items]
Available-for-sale, Less than 12 months - Gross unrealized losses	4	16
Available-for-sale, Less than 12 months - Estimated fair value	1,173	1,081
Available-for-sale, 12 months or more - Gross unrealized losses	38	224
Available-for-sale, 12 months or more - Estimated fair value	3,215	6,661
Available-for-sale, Total - Gross unrealized losses	42	240
Available-for-sale, Total - Estimated fair value	4,388	7,742
Small Business Administration Loan Backed Securities [Member]
Investment [Line Items]
Available-for-sale, Less than 12 months - Gross unrealized losses	1	19
Available-for-sale, Less than 12 months - Estimated fair value	172	1,180
Available-for-sale, 12 months or more - Gross unrealized losses	40	28
Available-for-sale, 12 months or more - Estimated fair value	1,215	711
Available-for-sale, Total - Gross unrealized losses	41	47
Available-for-sale, Total - Estimated fair value	$ 1,387	$ 1,891