Investment Securities (Investments, by type and length in continuous loss position) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Mortgage-backed Securities, Issued by Private Enterprises [Member] Residential Mortgage Backed Securities [Member]	Jun. 30, 2014 Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] Residential Mortgage Backed Securities [Member]	Jun. 30, 2014 Domestic Corporate Debt Securities [Member]	Dec. 31, 2013 Domestic Corporate Debt Securities [Member]	Jun. 30, 2014 US States and Political Subdivisions Debt Securities [Member]	Dec. 31, 2013 US States and Political Subdivisions Debt Securities [Member]	Jun. 30, 2014 Residential Mortgage Backed Securities [Member]	Dec. 31, 2013 Residential Mortgage Backed Securities [Member]	Jun. 30, 2014 Mortgage-backed Securities, Residential, Subprime, Financing Receivable [Member]	Jun. 30, 2014 Commercial Mortgage Backed Securities [Member]	Dec. 31, 2013 Commercial Mortgage Backed Securities [Member]	Jun. 30, 2014 Asset-backed Securities [Member]	Dec. 31, 2013 Asset-backed Securities [Member]	Jun. 30, 2014 Foreign Corporate Debt Securities [Member]	Dec. 31, 2013 Foreign Corporate Debt Securities [Member]	Jun. 30, 2014 Foreign Government Debt Securities [Member]	Dec. 31, 2013 Foreign Government Debt Securities [Member]	Jun. 30, 2014 US Treasury and Government [Member]	Dec. 31, 2013 US Treasury and Government [Member]	Jun. 30, 2014 Retained Interest [Member]	Dec. 31, 2013 Retained Interest [Member]	Jun. 30, 2014 Equity Securities [Member]	Dec. 31, 2013 Equity Securities [Member]	Jun. 30, 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							$ 234	$ 2,170	$ 115	$ 1,076	$ 47	$ 232		$ 5	$ 396	$ 3	$ 112	$ 20	$ 96	$ 984	$ 1,479	$ 0	$ 229	$ 7	$ 2	$ 46	$ 31	$ 1,461	$ 5,823
Gross unrealized losses, less than 12 months							(4)	(122)	(2)	(82)	(1)	(11)		0	(24)	0	(2)	0	(3)	(3)	(6)	0	(27)	0	0	(2)	(3)	(12)	(280)
Estimated fair value, 12 months or more							1,523	598	766	367	471	430		931	780	321	359	444	454	89	42	255	254	1	0	0	0	4,801	3,284
Gross unrealized losses, 12 months or more							(87)	(95)	(94)	(109)	(29)	(37)		(42)	(58)	(36)	(44)	(50)	(83)	0	(1)	(1)	0	0	0	0	0	(339)	(427)
Percent Of Gross Unrealized Losses, 12 Months Or More, Considered Investment Grade	70.00%		70.00%
OTTI Previously Recognized Through OCI On Securities Held, Gross Unrealized Losses			(66)
Marketable securities OTTI recorded in AOCI			4
Marketable Securities, Realized Loss, Other than Temporary Impairments, Amount		96		96
Incremental Charges On Previously Impaired Investment Securities		7
Proceeds from Sale of Available-for-sale Securities	1,198	6,284	2,547	9,925
Debt securities, Estimated fair value					$ 640	$ 1,238							$ 337