Investment Securities (Contractual maturities) (Details) $ in Millions	Jun. 30, 2015 USD ($)
Amortized cost
Within one year	$ 4,912
After one year through five years	4,134
After five years through ten years	4,726
After ten years	18,221
Estimated fair value
Within one year	5,577
After one year through five years	4,355
After five years through ten years	5,069
After ten years	$ 20,499