Investment Securities (Contractual Maturity Distribution Of Debt Securities) (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Available-for-sale, After one year through five years, Amortized Cost		$ 2,956
Available-for-sale, After five years through ten years, Amortized Cost		1,690
Available-for-sale, After ten years, Amortized Cost		6,332
Available-for-sale, Subtotal, Amortized Cost		10,978
Available-for-sale, After one year through five years, Fair Value		2,939
Available-for-sale, After five years through ten years, Fair Value		1,697
Available-for-sale, After ten years, Fair Value		6,220
Available-for-sale, Subtotal, Fair Value		10,856
Investment securities available-for-sale, Amortized Cost	[1]	11,061	$ 10,829
Investment securities available-for-sale, Fair Value	[1]	10,938	10,787
Held-to-maturity, After one year through five years, Net Carrying Amount		0
Held-to-maturity, After five years through ten years, Net Carrying Amount		17
Held-to-maturity, After ten years, Net Carrying Amount		1,249
Investment securities held-to-maturity, Net Carrying Amount		1,266	1,582
Held-to-maturity, After one year through five years, Fair Value		0
Held-to-maturity, After five years through ten years, Fair Value		17
Held-to-maturity, After ten years, Fair Value		1,229
Investment securities held-to-maturity, Fair Value		1,246
Equity and other non-debt securities
Investment securities available-for-sale, Amortized Cost		83	129
Investment securities available-for-sale, Fair Value		82	$ 129
Investment securities held-to-maturity, Net Carrying Amount		0
Investment securities held-to-maturity, Fair Value		$ 0

[1] Included auction-rate securities at amortized cost and fair value of $51 million and $49 million, respectively, as of December 31, 2017 and $55 million and $54 million, respectively, as of December 31, 2016.