Investment Securities (Schedule of Unrealized Loss on Investments) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	$ 9,386	$ 1,391
Available-for-sale Securities, Unrealized Loss Less than 12 months	(414)	(45)
Available-for-sale Securities, Fair value 12 months or longer	94	257
Available-for-sale Securities, Unrealized Loss 12 months or longer	(15)	(36)
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	9,006	1,011
Available-for-sale Securities, Unrealized Loss Less than 12 months	(385)	(6)
Available-for-sale Securities, Fair value 12 months or longer	4	39
Available-for-sale Securities, Unrealized Loss 12 months or longer	0	(2)
US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	1,419	244
Available-for-sale Securities, Unrealized Loss Less than 12 months	(54)	(1)
Available-for-sale Securities, Fair value 12 months or longer	0	0
Available-for-sale Securities, Unrealized Loss 12 months or longer	0	0
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	32	0
Available-for-sale Securities, Unrealized Loss Less than 12 months	0	0
Available-for-sale Securities, Fair value 12 months or longer	0	0
Available-for-sale Securities, Unrealized Loss 12 months or longer	0	0
Foreign Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	113	11
Available-for-sale Securities, Unrealized Loss Less than 12 months	(3)	0
Available-for-sale Securities, Fair value 12 months or longer	0	0
Available-for-sale Securities, Unrealized Loss 12 months or longer	0	0
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	6,688	493
Available-for-sale Securities, Unrealized Loss Less than 12 months	(316)	(2)
Available-for-sale Securities, Fair value 12 months or longer	3	23
Available-for-sale Securities, Unrealized Loss 12 months or longer	0	(1)
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	438	143
Available-for-sale Securities, Unrealized Loss Less than 12 months	(3)	(1)
Available-for-sale Securities, Fair value 12 months or longer	1	1
Available-for-sale Securities, Unrealized Loss 12 months or longer	0	0
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	316	120
Available-for-sale Securities, Unrealized Loss Less than 12 months	(9)	(2)
Available-for-sale Securities, Fair value 12 months or longer	0	15
Available-for-sale Securities, Unrealized Loss 12 months or longer	0	(1)
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	380	380
Available-for-sale Securities, Unrealized Loss Less than 12 months	(29)	(39)
Available-for-sale Securities, Fair value 12 months or longer	90	218
Available-for-sale Securities, Unrealized Loss 12 months or longer	$ (15)	$ (34)