Investment Securities (Narrative) (Details) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015 USD ($) Security	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) Security	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Securities with no credit impairment in unrealized loss position | Security		112		112
Securities gains		$ 0	$ 0	$ 0	$ 1
Securities losses		0	0	(2)	0
Net securities (losses) gains		0	$ 0	(2)	$ 1
Investment securities available-for-sale, Amortized Cost	[1]	8,201		8,201		$ 8,035
Investment securities available-for-sale, Fair Value	[1]	8,267		8,267		8,116
Investment securities held-to-maturity, Amortized Cost		1,952		1,952		1,935
Investment securities held-to-maturity, Fair Value		1,946		1,946
Carrying value of securities pledged		2,800		2,800
Liabilities secured by pledged collateral		$ 2,200		$ 2,200
Residential Mortgage-Backed Securities
Securities with no credit impairment in unrealized loss position | Security		93		93
Investment securities available-for-sale, Amortized Cost	[2]	$ 7,200		$ 7,200		7,192
Investment securities available-for-sale, Fair Value	[2]	7,262		7,262		7,274
Investment securities held-to-maturity, Amortized Cost	[2],[3]	1,952		1,952		1,935
Investment securities held-to-maturity, Fair Value	[2],[3]	$ 1,946		$ 1,946		1,933
Auction-Rate State And Municipal Securities
Securities with no credit impairment in unrealized loss position		17		17
Auction-Rate Corporate Debt Securities
Securities with no credit impairment in unrealized loss position | Security		1		1
Investment securities available-for-sale, Amortized Cost		$ 47		$ 47		51
Investment securities available-for-sale, Fair Value		$ 47		$ 47		51
U.S. Treasury and Other U.S. Government Agency Securities
Securities with no credit impairment in unrealized loss position		1		1
Investment securities available-for-sale, Amortized Cost		$ 729		$ 729		526
Investment securities available-for-sale, Fair Value		732		$ 732		526
Auction-Rate Securities
ARS portfolio redeemed or sold since acquisition				93.00%
ARS portfolio redeemed or sold since acquisition at or above cost				92.00%
Investment securities available-for-sale, Amortized Cost		95		$ 95		137
Investment securities available-for-sale, Fair Value		$ 95		$ 95		$ 136

[1] Included auction-rate securities at amortized cost and fair value of $95 million as of June 30, 2015 and $137 million and $136 million, respectively, as of December 31, 2014.

[2] Residential mortgage-backed securities 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 $19 million at June 30, 2015 and $23 million at December 31, 2014 related to securities transferred to available-for-sale, which are included in accumulated other comprehensive loss.