Investment Securities (Contractual maturities) (Details) $ in Millions	Jun. 30, 2015 USD ($)
Amortized Cost
Within one year	$ 4,909
After one year through five years	4,133
After five years through ten years	4,726
After ten years	18,221
Estimated Fair Value
Within one year	5,572
After one year through five years	4,354
After five years through ten years	5,069
After ten years	$ 20,499