Investment Securities (Details 1) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Available-for-sale investment securities with gross unrealized losses and length of time
Estimated Fair Value, Less than 12 months	$ 1,034	$ 100
Estimated Fair Value, 12 months or more	83	73
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Gross Unrealized Losses, Less than 12 months	(33)	(1)
Gross Unrealized Losses, 12 months or more	(12)	(4)
U.S. States and Political Subdivisions Debt Securities [Member]
Available-for-sale investment securities with gross unrealized losses and length of time
Estimated Fair Value, Less than 12 months	992	100
Estimated Fair Value, 12 months or more	66	73
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Gross Unrealized Losses, Less than 12 months	(32)	(1)
Gross Unrealized Losses, 12 months or more	(11)	(4)
Foreign government bonds and obligations [Member]
Available-for-sale investment securities with gross unrealized losses and length of time
Estimated Fair Value, Less than 12 months	42	0
Estimated Fair Value, 12 months or more	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Gross Unrealized Losses, Less than 12 months	(1)	0
Gross Unrealized Losses, 12 months or more	0	0
Other
Available-for-sale investment securities with gross unrealized losses and length of time
Estimated Fair Value, Less than 12 months	0	0
Estimated Fair Value, 12 months or more	17	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Gross Unrealized Losses, Less than 12 months	0	0
Gross Unrealized Losses, 12 months or more	$ (1)	$ 0