Investment Securities (Schedule of Unrealized Loss on Investments) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	$ 3,574	$ 1,391
Available-for-sale Securities, Unrealized Loss Less than 12 months	(49)	(45)
Available-for-sale Securities, Fair value 12 months or longer	174	257
Available-for-sale Securities, Unrealized Loss 12 months or longer	(22)	(36)
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	3,357	1,011
Available-for-sale Securities, Unrealized Loss Less than 12 months	(22)	(6)
Available-for-sale Securities, Fair value 12 months or longer	18	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	724	244
Available-for-sale Securities, Unrealized Loss Less than 12 months	(1)	(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	0	11
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
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Fair value Less than 12 months	2,360	493
Available-for-sale Securities, Unrealized Loss Less than 12 months	(18)	(2)
Available-for-sale Securities, Fair value 12 months or longer	11	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	163	143
Available-for-sale Securities, Unrealized Loss Less than 12 months	(1)	(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	110	120
Available-for-sale Securities, Unrealized Loss Less than 12 months	(2)	(2)
Available-for-sale Securities, Fair value 12 months or longer	6	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	217	380
Available-for-sale Securities, Unrealized Loss Less than 12 months	(27)	(39)
Available-for-sale Securities, Fair value 12 months or longer	156	218
Available-for-sale Securities, Unrealized Loss 12 months or longer	$ (22)	$ (34)