Investment Securities (Summary Of Investment Securities) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Investment [Line Items]
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost	$ 252
Held-to-maturity, fair value	762
Debt Securities, Available-for-sale, Amortized Cost	15,045	$ 15,040
Available-For-Sale Debt Securities, Gross Unrealized Gains, Recognized In O C I		23
Available-For-Sale Debt Securities, Gross Unrealized Losses, Recognized In O C I		326
Debt Securities, Available-for-sale	14,904	14,737
Available-for-sale Securities, Gross Unrealized Gain	55
Available-for-sale, Amortized cost	15,045
Available-for-sale, Gross unrealized losses, Recognized in OCI	196
Available-for-sale securities, Estimated fair value	14,904	14,737
amortized cost of investment securities	15,809	15,814
Gross Unrealized Gains of Investment Securities Recognized in OCI	59	27
Gross Unrealized Losses of Investment Securities Recognized in OCI	202	337
Estimated Fair Value of Investment Securities	15,666	15,504
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value	252
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost	2,147
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value	2,125
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost	329
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value	328
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Amortized Cost	5,984
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value	5,928
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Rolling after Five Through Ten Years, Amortized Cost	132
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	132
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost	4,441
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	4,406
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost	51
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value	50
Debt Securities, Available-for-sale, Allocated and Single Maturity Date, Maturity, after 10 Years, Amortized Cost	2,473
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value	2,445
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Amortized Cost	764
Available-for-sale, Other debt securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	25	25
Available-For-Sale Debt Securities, Gross Unrealized Gains, Recognized In O C I	0	0
Available-For-Sale Debt Securities, Gross Unrealized Losses, Recognized In O C I	3	4
Debt Securities, Available-for-sale	22	21
Small Business Administration Loan Backed Securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,919	2,042
Available-For-Sale Debt Securities, Gross Unrealized Gains, Recognized In O C I	1	1
Available-For-Sale Debt Securities, Gross Unrealized Losses, Recognized In O C I	43	47
Debt Securities, Available-for-sale	1,877	1,996
Agency Guaranteed Mortgage Backed Securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	10,384	10,236
Available-For-Sale Debt Securities, Gross Unrealized Gains, Recognized In O C I	36	18
Available-For-Sale Debt Securities, Gross Unrealized Losses, Recognized In O C I	136	240
Debt Securities, Available-for-sale	10,284	10,014
Agency Securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,407	1,394
Available-For-Sale Debt Securities, Gross Unrealized Gains, Recognized In O C I	2	0
Available-For-Sale Debt Securities, Gross Unrealized Losses, Recognized In O C I	11	19
Debt Securities, Available-for-sale	1,398	1,375
US Treasury Securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	40	40
Available-For-Sale Debt Securities, Gross Unrealized Gains, Recognized In O C I	0	0
Available-For-Sale Debt Securities, Gross Unrealized Losses, Recognized In O C I	0	0
Debt Securities, Available-for-sale	40	40
US States and Political Subdivisions Debt Securities [Member]
Investment [Line Items]
Held-to-maturity, fair value	762	767
Held-to-maturity, Amortized cost	764	774
Debt Securities, Available-for-sale, Amortized Cost	1,270	1,303
Available-For-Sale Debt Securities, Gross Unrealized Gains, Recognized In O C I	16	4
Available-For-Sale Debt Securities, Gross Unrealized Losses, Recognized In O C I	3	16
Debt Securities, Available-for-sale	1,283	1,291
Held-to-maturity Securities, Unrecognized Holding Gain (Deprecated 2018-01-31)	4	4
Held-to-maturity Securities, Unrecognized Holding Loss (Deprecated 2018-01-31)	$ 6	$ 11