Investment Securities (Contractual maturities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013
Investment [Line Items]
Within one year	$ 2,397
After one year through five years	3,303
After five years through ten years	4,984
After ten years	18,024
Within one year	2,417
After one year through five years	3,506
After five years through ten years	5,156
After ten years	$ 19,901