Investment Securities (Investments, by type and length in continuous loss position) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Mortgage-backed Securities, Issued by Private Enterprises [Member] Residential Mortgage Backed Securities [Member]	Mar. 31, 2014 Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] Residential Mortgage Backed Securities [Member]	Mar. 31, 2014 Domestic Corporate Debt Securities [Member]	Dec. 31, 2013 Domestic Corporate Debt Securities [Member]	Mar. 31, 2014 US States and Political Subdivisions Debt Securities [Member]	Dec. 31, 2013 US States and Political Subdivisions Debt Securities [Member]	Mar. 31, 2014 Residential Mortgage Backed Securities [Member]	Dec. 31, 2013 Residential Mortgage Backed Securities [Member]	Mar. 31, 2014 Mortgage-backed Securities, Residential, Subprime, Financing Receivable [Member]	Mar. 31, 2014 Commercial Mortgage Backed Securities [Member]	Dec. 31, 2013 Commercial Mortgage Backed Securities [Member]	Mar. 31, 2014 Asset-backed Securities [Member]	Dec. 31, 2013 Asset-backed Securities [Member]	Mar. 31, 2014 Foreign Corporate Debt Securities [Member]	Dec. 31, 2013 Foreign Corporate Debt Securities [Member]	Mar. 31, 2014 Foreign Government Debt Securities [Member]	Dec. 31, 2013 Foreign Government Debt Securities [Member]	Mar. 31, 2014 US Treasury and Government [Member]	Dec. 31, 2013 US Treasury and Government [Member]	Mar. 31, 2014 Retained Interest [Member]	Dec. 31, 2013 Retained Interest [Member]	Mar. 31, 2014 Equity Securities [Member]	Dec. 31, 2013 Equity Securities [Member]	Mar. 31, 2014 Total [Member]	Dec. 31, 2013 Total [Member]
Available-for-sale Securities Estimated Fair Value And Gross Unrealized Losses [Abstract]
Estimated fair value, less than 12 months					$ 1,578	$ 2,170	$ 942	$ 1,076	$ 187	$ 232		$ 254	$ 396	$ 101	$ 112	$ 43	$ 96	$ 1,098	$ 1,479	$ 238	$ 229	$ 1	$ 2	$ 40	$ 31	$ 4,482	$ 5,823
Gross unrealized losses, less than 12 months					(63)	(122)	(37)	(82)	(6)	(11)		(11)	(24)	(1)	(2)	(1)	(3)	(3)	(6)	(18)	(27)	0	0	(8)	(3)	(148)	(280)
Estimated fair value, 12 months or more					563	598	347	367	430	430		803	780	294	359	430	454	52	42	0	254	1	0	0	0	2,920	3,284
Gross unrealized losses, 12 months or more					(75)	(95)	(93)	(109)	(33)	(37)		(50)	(58)	(40)	(44)	(63)	(83)	0	(1)	0	0	0	0	0	0	(354)	(427)
Percent Of Gross Unrealized Losses, 12 Months Or More, Considered Investment Grade	70.00%
OTTI Previously Recognized Through OCI On Securities Held, Gross Unrealized Losses	85
Marketable securities OTTI recorded in AOCI	4
Marketable Securities, Realized Loss, Other than Temporary Impairments, Amount	34	278
Proceeds from Sale of Available-for-sale Securities	1,349	3,641
Debt securities, Estimated fair value			$ 649	$ 1,225							$ 355