Investment Securities (Details 1) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 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	$ 1,347	$ 100
Estimated Fair Value, 12 months or more	85	73
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Gross Unrealized Losses, Less than 12 months	(59)	(1)
Gross Unrealized Losses, 12 months or more	(11)	(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	1,274	100
Estimated Fair Value, 12 months or more	68	73
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Gross Unrealized Losses, Less than 12 months	(57)	(1)
Gross Unrealized Losses, 12 months or more	(10)	(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	52	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 [Member]
Available-for-sale investment securities with gross unrealized losses and length of time
Estimated Fair Value, Less than 12 months	21	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	(1)	0
Gross Unrealized Losses, 12 months or more	$ (1)	$ 0