Investment Securities (Schedule of Unrealized Loss on Investments) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	$ 8,992	$ 10,118
Available-for-sale Securities, Unrealized Loss Less than 12 months	(331)	(482)
Available-for-sale Securities, Fair value 12 months or longer	309	204
Available-for-sale Securities, Unrealized Loss 12 months or longer	(28)	(26)
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	8,712	9,951
Available-for-sale Securities, Unrealized Loss Less than 12 months	(314)	(470)
Available-for-sale Securities, Fair value 12 months or longer	252	104
Available-for-sale Securities, Unrealized Loss 12 months or longer	(22)	(10)
US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	1,227	1,405
Available-for-sale Securities, Unrealized Loss Less than 12 months	(46)	(69)
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	24	212
Available-for-sale Securities, Unrealized Loss Less than 12 months	0	(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
Foreign Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	40	114
Available-for-sale Securities, Unrealized Loss Less than 12 months	(1)	(3)
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	6,886	7,503
Available-for-sale Securities, Unrealized Loss Less than 12 months	(263)	(388)
Available-for-sale Securities, Fair value 12 months or longer	247	100
Available-for-sale Securities, Unrealized Loss 12 months or longer	(22)	(10)
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	387	407
Available-for-sale Securities, Unrealized Loss Less than 12 months	(2)	(3)
Available-for-sale Securities, Fair value 12 months or longer	0	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	148	310
Available-for-sale Securities, Unrealized Loss Less than 12 months	(2)	(6)
Available-for-sale Securities, Fair value 12 months or longer	5	3
Available-for-sale Securities, Unrealized Loss 12 months or longer	0	0
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	280	167
Available-for-sale Securities, Unrealized Loss Less than 12 months	(17)	(12)
Available-for-sale Securities, Fair value 12 months or longer	57	100
Available-for-sale Securities, Unrealized Loss 12 months or longer	$ (6)	$ (16)