Investment Securities (Summary Of Investment Securities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Investment [Line Items]
Held-to-maturity, fair value	$ 762
Available-for-sale debt securities, Amortized cost	15,241	$ 13,337
Available-for-sale debt securities, Gross unrealized gains, Recognized in OCI	29	18
Available-for-sale debt securities, Gross unrealized losses, Recognized in OCI	181	167
Available-for-sale debt securities, Estimated fair value	15,089	13,188
Available-for-sale, at fair value	15,161	13,372
Available-for-sale Securities, Amortized Cost Basis	15,313	13,521
Available-for-sale, Gross unrealized gains, Recognized in OCI	29	18
Available-for-sale, Gross unrealized losses, Recognized in OCI	181	167
amortized cost of investment securities	16,083	14,389
Gross Unrealized Gains of Investment Securities Recognized in OCI	34	23
Gross Unrealized Losses of Investment Securities Recognized in OCI	194	190
Estimated Fair Value of Investment Securities	15,923	14,222
Municipal Securities [Member]
Investment [Line Items]
Held-to-maturity, fair value	762	850
Held-to-maturity, Amortized cost	770	868
Available-for-sale debt securities, Amortized cost	1,336	1,182
Available-for-sale debt securities, Gross unrealized gains, Recognized in OCI	9	1
Available-for-sale debt securities, Gross unrealized losses, Recognized in OCI	11	29
Available-for-sale debt securities, Estimated fair value	1,334	1,154
Held-to-maturity Securities, Unrecognized Holding Gain	5	5
Held-to-maturity Securities, Unrecognized Holding Loss	13	23
US Treasury Securities [Member]
Investment [Line Items]
Available-for-sale debt securities, Amortized cost	25	0
Available-for-sale debt securities, Gross unrealized gains, Recognized in OCI	0	0
Available-for-sale debt securities, Gross unrealized losses, Recognized in OCI	0	0
Available-for-sale debt securities, Estimated fair value	25	0
Available-for-sale, Other debt securities [Member]
Investment [Line Items]
Available-for-sale debt securities, Amortized cost	25	25
Available-for-sale debt securities, Gross unrealized gains, Recognized in OCI	0	0
Available-for-sale debt securities, Gross unrealized losses, Recognized in OCI	1	1
Available-for-sale debt securities, Estimated fair value	24	24
Agency Securities [Member]
Investment [Line Items]
Available-for-sale debt securities, Amortized cost	1,830	1,846
Available-for-sale debt securities, Gross unrealized gains, Recognized in OCI	1	2
Available-for-sale debt securities, Gross unrealized losses, Recognized in OCI	13	9
Available-for-sale debt securities, Estimated fair value	1,818	1,839
Agency Guaranteed Mortgage-Backed Securities [Member]
Investment [Line Items]
Available-for-sale debt securities, Amortized cost	9,798	7,986
Available-for-sale debt securities, Gross unrealized gains, Recognized in OCI	9	7
Available-for-sale debt securities, Gross unrealized losses, Recognized in OCI	141	110
Available-for-sale debt securities, Estimated fair value	9,666	7,883
Small Business Administration Loan-Backed Securities [Member]
Investment [Line Items]
Available-for-sale debt securities, Amortized cost	2,227	2,298
Available-for-sale debt securities, Gross unrealized gains, Recognized in OCI	10	8
Available-for-sale debt securities, Gross unrealized losses, Recognized in OCI	15	18
Available-for-sale debt securities, Estimated fair value	2,222	2,288
Mutual Funds And Stock [Member]
Investment [Line Items]
Available-for-sale, at fair value	72	184
Available-for-sale Securities, Amortized Cost Basis	72	184
Available-for-sale, Gross unrealized gains, Recognized in OCI	0	0
Available-for-sale, Gross unrealized losses, Recognized in OCI	$ 0	$ 0