Investment Securities (Narrative) (Details) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2016 USD ($) Security	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) Security	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Securities with no credit impairment in unrealized loss position | Security		95		95
Securities gains		$ 0	$ 0	$ 0	$ 0
Securities losses		0	$ 0	3	$ 2
Investment securities available-for-sale, Amortized Cost	[1]	10,621		10,621		$ 10,491
Investment securities available-for-sale, Fair Value	[1]	10,789		10,789		10,519
Investment securities held-to-maturity, Amortized Cost		1,695		1,695		1,981
Investment securities held-to-maturity, Fair Value		1,713		1,713
Carrying value of securities pledged		1,500		1,500
Liabilities secured by pledged collateral		$ 1,000		$ 1,000
Residential mortgage-backed securities
Securities with no credit impairment in unrealized loss position | Security		52		52
Investment securities available-for-sale, Amortized Cost	[2]	$ 7,714		$ 7,714		7,513
Investment securities available-for-sale, Fair Value	[2]	7,828		7,828		7,545
Investment securities held-to-maturity, Amortized Cost	[2],[3]	1,695		1,695		1,981
Investment securities held-to-maturity, Fair Value	[2],[3]	$ 1,713		$ 1,713		1,973
Auction Rate Preferred Securities
Securities with no credit impairment in unrealized loss position		28		28
Auction-Rate State And Municipal Securities
Securities with no credit impairment in unrealized loss position		15		15
Auction-rate securities
ARS portfolio redeemed or sold since acquisition				96.00%
ARS portfolio redeemed or sold since acquisition at or above cost				90.00%
Investment securities available-for-sale, Amortized Cost		$ 56		$ 56		76
Investment securities available-for-sale, Fair Value		54		54		$ 77
Prepayment options | Residential mortgage-backed securities
Investment securities available-for-sale, Amortized Cost		7,700		7,700
Investment securities available-for-sale, Fair Value		7,800		7,800
Investment securities held-to-maturity, Amortized Cost		1,700		1,700
Investment securities held-to-maturity, Fair Value		$ 1,700		$ 1,700

[1] Included auction-rate securities at amortized cost and fair value of $56 million and $54 million, respectively as of September 30, 2016 and $76 million and $77 million, respectively, as of December 31, 2015.

[2] Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises.

[3] The amortized cost of investment securities held-to-maturity included net unrealized losses of $13 million at September 30, 2016 and $15 million at December 31, 2015 related to securities transferred from available-for-sale, which are included in accumulated other comprehensive loss.