Borrowings and Contractual Commitments Borrowings and Contractual Commitments - Additional Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Debt Instrument [Line Items]
Short-term Debt, Average Outstanding Amount	$ 7,000,000,000		$ 3,500,000,000
Short-term Debt, Maximum Month-end Outstanding Amount	10,700,000,000		9,000,000,000
Long-term Debt	9,357,000,000	[1]	10,908,000,000	[1]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	295,000,000
Long-term Debt, Maturities, Repayments of Principal in Year Two	19,000,000
Long-term Debt, Maturities, Repayments of Principal in Year Three	835,000,000
Long-term Debt, Maturities, Repayments of Principal in Year Four	1,200,000,000
Long-term Debt, Maturities, Repayments of Principal in Year Five	4,700,000,000
Long-term Debt, Maturities, Repayments of Principal after Year Five	2,300,000,000
Tier One Risk Based Capital	14,975,000,000		14,490,000,000
Other Short-term Borrowings	3,303,000,000		8,983,000,000
Debt Instrument, Repurchase Amount	1,200,000,000
Gains (Losses) on Extinguishment of Debt	(16,000,000)		3,000,000		(70,000,000)
Long-term Debt [Member]
Debt Instrument [Line Items]
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	627,000,000
Tier One Risk Based Capital			1,900,000,000
Tier Two Risk Based Capital	1,500,000,000		1,600,000,000
Federal Reserve Bank Advances [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	23,800,000,000
Federal Home Loan Bank Advances [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	16,000,000,000
Senior Notes [Member]
Debt Instrument [Line Items]
Extinguishment of Debt, Amount	1,200,000,000
Debt Denominated in U.S. Currency [Member]
Debt Instrument [Line Items]
Maturities of Senior Debt	1,400,000,000
Debt Denominated in Foreign Currency [Member]
Debt Instrument [Line Items]
Long-term Debt	0		460,000,000
Maturities of Senior Debt	589,000,000
Government Guaranteed Debt Under The Temporary Liquidity Guarantee Program [Member]
Debt Instrument [Line Items]
Long-term Debt	0		576,000,000
Federal Home Loan Bank Advances [Member]
Debt Instrument [Line Items]
Long-term Debt	3,000,000,000
Extinguishment of Debt, Amount	1,000,000,000
Federal Home Loan Bank Advances [Member]
Debt Instrument [Line Items]
Federal Home Loan Bank, Advances, Short-term	1,500,000,000
Other Short-term Borrowings	$ 1,500,000,000		$ 7,000,000,000

[1] 3 Includes debt of consolidated VIEs ($286 and $289 at fair value as of December 31, 2012 and December 31, 2011, respectively)666 722