Deposits and Borrowings - Deposits and Short-term Borrowings (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Deposits:
Non-interest bearing deposits	$ 25,847	$ 25,081
Interest-bearing deposits	191,874	180,467
Total deposits	217,721	205,548	$ 204,523
Short-term Debt [Line Items]
Short-term borrowings	981	17,080
Federal funds purchased and securities loaned or sold under agreements to repurchase
Short-term Debt [Line Items]
Short-term borrowings	981	880
Federal Home Loan Bank Advances
Short-term Debt [Line Items]
Short-term borrowings	$ 0	$ 16,200