Investment Securities (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended
	Dec. 31, 2014		Dec. 31, 2014		Dec. 31, 2013
Available-for-sale securities transferred to held-to-maturity	$ 1,958,000,000
Unrealized losses on available-for-sale securities transferred to held-to-maturity	23,000,000
Securities with no credit impairment in unrealized loss position	142		142
ARS portfolio redeemed or sold since acquisition			89.00%
ARS portfolio redeemed or sold since acquisition at or above cost			95.00%
Amortized cost available-for-sale securities	7,793,000,000		7,793,000,000
Investment securities available-for-sale	8,116,000,000	[1]	8,116,000,000	[1]	9,307,000,000	[1]
Held-to-maturity securities, Amortized Cost	1,935,000,000	[2]	1,935,000,000	[2]	0
Held-to-maturity Securities, Fair Value	1,933,000,000		1,933,000,000
Carrying value of securities pledged	2,900,000,000		2,900,000,000
Liabilities secured by pledged collateral	1,900,000,000		1,900,000,000
Residential mortgage-backed securities
Securities with no credit impairment in unrealized loss position	80		80
Amortized cost available-for-sale securities	7,200,000,000		7,200,000,000
Investment securities available-for-sale	7,274,000,000	[2]	7,274,000,000	[2]	8,926,000,000	[2]
Held-to-maturity securities, Amortized Cost	1,935,000,000	[2],[3]	1,935,000,000	[2],[3]
Held-to-maturity Securities, Fair Value	1,933,000,000	[2],[3]	1,933,000,000	[2],[3]
Auction-Rate Preferred Securities
Securities with no credit impairment in unrealized loss position	43		43
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	1		1
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	526,000,000		526,000,000		45,000,000
Equity and Other Non-Debt Securities
Investment securities available-for-sale	242,000,000		242,000,000		258,000,000
Auction-Rate Securities
Investment securities available-for-sale	$ 136,000,000		$ 136,000,000		$ 159,000,000

[1] Included auction-rate securities at amortized cost and fair value of $137 million and $136 million, respectively, as of December 31, 2014 and $169 million and $159 million, respectively, as of December 31, 2013.

[2] Residential mortgage-backed securities issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises.

[3] Investment securities transferred from available-for-sale are reclassified at fair value at the time of transfer. The amortized cost of investment securities held-to-maturity included gross unrealized gains of $9 million and gross unrealized losses of $32 million at December 31, 2014 related to securities transferred, which are included in accumulated other comprehensive loss.