Securities (Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Securities
AFS securities, debt securities due in one year or less, amortized cost	$ 491
AFS securities, debt securities due in one year or less, fair value	491
AFS securities, debt securities due after one year through five years, amortized cost	807
AFS securities, debt securities due after one year through five years, fair value	819
AFS securities, debt securities due after five years through ten years, amortized cost	545
AFS securities, debt securities due after five years through ten years, fair value	577
AFS securities, debt securities due after ten years, amortized cost	18,894
AFS securities, debt securities due after ten years, fair value	19,049
Total AFS debt securities, amortized cost	20,737
Total AFS debt securities, fair value	20,936
HTM securities, debt securities due after one year through five years, amortized cost	1
HTM securities, debt securities due after one year through five years, fair value	1
HTM securities, debt securities due after five years through ten years, amortized cost	6,639
HTM securities, debt securities due after five years through ten years, fair cost	6,467
HTM securities, debt securities due after ten years, amortized cost	13,792
HTM securities, debt securities due after ten years, fair value	13,796
HTM securities, amortized cost	20,432	18,101
Held-to-maturity Securities, Fair Value	$ 20,264	$ 17,530