Deposits and Borrowings - Deposits and Short-term Borrowings (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Deposits:
Non-interest bearing deposits	$ 25,388	$ 22,643
Interest-bearing deposits	178,876	181,880
Total deposits	204,264	204,523	206,834
Short-term Debt [Line Items]
Short-term borrowings	12,130	16,215
Federal funds purchased and securities loaned or sold under agreements to repurchase
Short-term Debt [Line Items]
Short-term borrowings	2,330	915
FHLB advances
Short-term Debt [Line Items]
Short-term borrowings	$ 9,800	$ 15,300