Fair Value Measurement - Carrying Value and Estimated Fair Value (Details 7) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Due from Banks	$ 53,723,000,000	$ 59,602,000,000	$ 27,567,000,000	$ 26,206,000,000
Interest-bearing Deposits in Banks and Other Financial Institutions	121,814,000,000	85,279,000,000
Financial assets
Federal funds sold and securities purchased under resale agreements (included $24.2 and $20.3 at fair value)	296,296,000,000	235,314,000,000
Financial liabilities
Commercial Paper	55,367,000,000	51,631,000,000
Other Short-term Borrowings	26,636,000,000	21,908,000,000
Beneficial interest liability, at fair value	63,191,000,000	65,977,000,000
Trading assets and liabilities average balances Abstract
Trading assets - debt and equity instruments	349,337,000,000	393,890,000,000	354,441,000,000
Trading assets - derivative receivables	85,744,000,000	90,003,000,000	84,676,000,000
Trading liabilities - debt and equity instruments	69,001,000,000	81,916,000,000	78,159,000,000
Trading liabilities - derivative payables	76,162,000,000	71,539,000,000	65,714,000,000
Carrying value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Due from Banks	53,700,000,000	59,600,000,000
Interest-bearing Deposits in Banks and Other Financial Institutions	121,800,000,000	85,300,000,000
Financial assets
Accrued interest and accounts receivable	60,900,000,000	61,500,000,000
Federal funds sold and securities purchased under resale agreements (included $24.2 and $20.3 at fair value)	272,000,000,000	213,100,000,000
Securities borrowed (included $15.3 and $14.0 at fair value)	108,800,000,000	127,200,000,000
Loans (included $2.1 and $2.0 at fair value)	709,300,000,000	694,000,000,000
Other Assets, Fair Value Disclosure	49,700,000,000	49,800,000,000
Financial liabilities
Deposits (included $4.9 and $4.4 at fair value)	1,187,900,000,000	1,122,900,000,000
Federal funds purchased and securities loaned or sold under repurchase agreements	235,700,000,000	206,700,000,000
Commercial Paper	55,400,000,000	51,600,000,000
Other Short-term Borrowings	15,000,000,000	12,300,000,000
Accounts payable and other liabilities (included $0.1 and $0.2 at fair value)	156,500,000,000	166,900,000,000
Beneficial interest liability, at fair value	62,000,000,000	64,700,000,000
Long-term debt and junior subordinated deferrable interest debentures (included $34.7 and $38.8 at fair value)	218,200,000,000	222,100,000,000
Wholesale lending related commitments	700,000,000	700,000,000
Estimate of Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Due from Banks	53,700,000,000	59,600,000,000
Interest-bearing Deposits in Banks and Other Financial Institutions	121,800,000,000	85,300,000,000
Financial assets
Accrued interest and accounts receivable	60,900,000,000	61,500,000,000
Federal funds sold and securities purchased under resale agreements (included $24.2 and $20.3 at fair value)	272,000,000,000	213,100,000,000
Securities borrowed (included $15.3 and $14.0 at fair value)	108,800,000,000	127,200,000,000
Loans (included $2.1 and $2.0 at fair value)	711,800,000,000	693,700,000,000
Other Assets, Fair Value Disclosure	50,100,000,000	50,300,000,000
Financial liabilities
Deposits (included $4.9 and $4.4 at fair value)	1,188,400,000,000	1,123,400,000,000
Federal funds purchased and securities loaned or sold under repurchase agreements	235,700,000,000	206,700,000,000
Commercial Paper	55,400,000,000	51,600,000,000
Other Short-term Borrowings	15,000,000,000	12,300,000,000
Accounts payable and other liabilities (included $0.1 and $0.2 at fair value)	156,300,000,000	166,800,000,000
Beneficial interest liability, at fair value	62,100,000,000	64,900,000,000
Long-term debt and junior subordinated deferrable interest debentures (included $34.7 and $38.8 at fair value)	225,400,000,000	219,500,000,000
Wholesale lending related commitments	1,900,000,000	3,400,000,000
Estimate of Fair Value | Estimate of Fair Value, Level 1 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Due from Banks	53,700,000,000
Interest-bearing Deposits in Banks and Other Financial Institutions	114,100,000,000
Financial assets
Accrued interest and accounts receivable	0
Federal funds sold and securities purchased under resale agreements (included $24.2 and $20.3 at fair value)	0
Securities borrowed (included $15.3 and $14.0 at fair value)	0
Loans (included $2.1 and $2.0 at fair value)	0
Other Assets, Fair Value Disclosure	0
Financial liabilities
Deposits (included $4.9 and $4.4 at fair value)	0
Federal funds purchased and securities loaned or sold under repurchase agreements	0
Commercial Paper	0
Other Short-term Borrowings	0
Accounts payable and other liabilities (included $0.1 and $0.2 at fair value)	0
Beneficial interest liability, at fair value	0
Long-term debt and junior subordinated deferrable interest debentures (included $34.7 and $38.8 at fair value)	0
Wholesale lending related commitments	0
Estimate of Fair Value | Estimate of Fair Value, Level 2 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Due from Banks	0
Interest-bearing Deposits in Banks and Other Financial Institutions	7,700,000,000
Financial assets
Accrued interest and accounts receivable	60,300,000,000
Federal funds sold and securities purchased under resale agreements (included $24.2 and $20.3 at fair value)	272,000,000,000
Securities borrowed (included $15.3 and $14.0 at fair value)	108,800,000,000
Loans (included $2.1 and $2.0 at fair value)	26,400,000,000
Other Assets, Fair Value Disclosure	42,700,000,000
Financial liabilities
Deposits (included $4.9 and $4.4 at fair value)	1,187,200,000,000
Federal funds purchased and securities loaned or sold under repurchase agreements	235,700,000,000
Commercial Paper	55,400,000,000
Other Short-term Borrowings	15,000,000,000
Accounts payable and other liabilities (included $0.1 and $0.2 at fair value)	153,800,000,000
Beneficial interest liability, at fair value	57,700,000,000
Long-term debt and junior subordinated deferrable interest debentures (included $34.7 and $38.8 at fair value)	220,000,000,000
Wholesale lending related commitments	0
Estimate of Fair Value | Estimate of Fair Value, Level 3 Inputs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Due from Banks	0
Interest-bearing Deposits in Banks and Other Financial Institutions	0
Financial assets
Accrued interest and accounts receivable	600,000,000
Federal funds sold and securities purchased under resale agreements (included $24.2 and $20.3 at fair value)	0
Securities borrowed (included $15.3 and $14.0 at fair value)	0
Loans (included $2.1 and $2.0 at fair value)	685,400,000,000
Other Assets, Fair Value Disclosure	7,400,000,000
Financial liabilities
Deposits (included $4.9 and $4.4 at fair value)	1,200,000,000
Federal funds purchased and securities loaned or sold under repurchase agreements	0
Commercial Paper	0
Other Short-term Borrowings	0
Accounts payable and other liabilities (included $0.1 and $0.2 at fair value)	2,500,000,000
Beneficial interest liability, at fair value	4,400,000,000
Long-term debt and junior subordinated deferrable interest debentures (included $34.7 and $38.8 at fair value)	5,400,000,000
Wholesale lending related commitments	$ 1,900,000,000