Fair Value Measurement - Carrying Value and Estimated Fair Value (Details 7) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011
Financial assets
Cash and due from banks	$ 45,524,000,000	$ 55,383,000,000	$ 53,723,000,000	$ 59,602,000,000
Deposits with banks	257,635,000,000		121,814,000,000
Federal funds sold and securities purchased under resale agreements (included $32,862 and $24,891 at fair value)	218,343,000,000		296,296,000,000
Mortgage servicing rights at fair value	7,949,000,000	8,039,000,000	7,614,000,000	7,223,000,000
Financial liabilities
Commercial paper	58,835,000,000		55,367,000,000
Other Short-term Borrowings	27,200,000,000		26,636,000,000
Beneficial interest liability, at fair value	58,300,000,000		63,191,000,000
Trading assets and liabilities average balances Abstract
Trading assets - debt and equity instruments	370,694,000,000	355,335,000,000
Trading assets - derivative receivables	74,918,000,000	90,446,000,000
Trading liabilities - debt and equity instruments	70,506,000,000	68,984,000,000
Trading liabilities - derivative payables	68,683,000,000	76,069,000,000
Fair Value, Measurements, Recurring [Member]
Financial assets
Trading assets	430,991,000,000		450,028,000,000
Mortgage servicing rights at fair value	7,949,000,000		7,614,000,000
Financial liabilities
Trading liabilities	125,726,000,000		131,918,000,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Financial assets
Securities borrowed	0		0
Trading assets	44,560,000,000		48,897,000,000
Loans, at fair value	2,064,000,000		2,282,000,000
Mortgage servicing rights at fair value	7,949,000,000		7,614,000,000
Financial liabilities
Deposits	2,015,000,000		1,983,000,000
Federal funds purchased and securities loaned or sold under repurchase agreements (included $9.5 and $4.1 at fair value)	0		0
Other Short-term Borrowings	2,137,000,000		1,619,000,000
Trading liabilities	20,334,000,000		21,570,000,000
Accounts payable and other liabilities	33,000,000		36,000,000
Long-term debt and junior subordinated deferrable interest debentures	9,084,000,000		8,476,000,000
Fair value | Fair Value, Measurements, Recurring [Member]
Financial assets
Securities borrowed	5,411,000,000		10,177,000,000
Loans, at fair value	2,161,000,000		2,555,000,000
Financial liabilities
Deposits	6,029,000,000		5,733,000,000
Federal funds purchased and securities loaned or sold under repurchase agreements (included $9.5 and $4.1 at fair value)	4,380,000,000		4,388,000,000
Other Short-term Borrowings	13,818,000,000		11,591,000,000
Accounts payable and other liabilities	33,000,000		36,000,000
Long-term debt and junior subordinated deferrable interest debentures	30,655,000,000		30,788,000,000
Carrying value
Financial assets
Cash and due from banks	45,500,000,000		53,700,000,000
Deposits with banks	257,600,000,000		121,800,000,000
Accrued interest and accounts receivable	74,200,000,000		60,900,000,000
Federal funds sold and securities purchased under resale agreements (included $32,862 and $24,891 at fair value)	192,700,000,000		272,000,000,000
Securities borrowed	108,600,000,000		108,800,000,000
Loans, at fair value	705,900,000,000		709,300,000,000
Total other assets	50,900,000,000		49,700,000,000
Financial liabilities
Deposits	1,196,500,000,000		1,187,900,000,000
Federal funds purchased and securities loaned or sold under repurchase agreements (included $9.5 and $4.1 at fair value)	243,900,000,000		235,700,000,000
Commercial paper	58,800,000,000		55,400,000,000
Other Short-term Borrowings	13,400,000,000		15,000,000,000
Accounts payable and other liabilities	160,900,000,000		156,500,000,000
Beneficial interest liability, at fair value	57,200,000,000		62,000,000,000
Long-term debt and junior subordinated deferrable interest debentures	237,700,000,000		218,200,000,000
Wholesale lending related commitments	700,000,000		700,000,000
Estimate of Fair Value
Financial assets
Cash and due from banks	45,500,000,000		53,700,000,000
Deposits with banks	257,600,000,000		121,800,000,000
Accrued interest and accounts receivable	74,200,000,000		60,900,000,000
Federal funds sold and securities purchased under resale agreements (included $32,862 and $24,891 at fair value)	192,700,000,000		272,000,000,000
Securities borrowed	108,600,000,000		108,800,000,000
Loans, at fair value	707,500,000,000		711,800,000,000
Total other assets	51,400,000,000		50,100,000,000
Financial liabilities
Deposits	1,196,900,000,000		1,188,400,000,000
Federal funds purchased and securities loaned or sold under repurchase agreements (included $9.5 and $4.1 at fair value)	243,900,000,000		235,700,000,000
Commercial paper	58,800,000,000		55,400,000,000
Other Short-term Borrowings	13,400,000,000		15,000,000,000
Accounts payable and other liabilities	160,800,000,000		156,300,000,000
Beneficial interest liability, at fair value	57,300,000,000		62,100,000,000
Long-term debt and junior subordinated deferrable interest debentures	244,700,000,000		225,400,000,000
Wholesale lending related commitments	1,400,000,000		1,900,000,000
Estimate of Fair Value | EstimateOfFairValueLevel1Inputs [Member]
Financial assets
Cash and due from banks	45,500,000,000		53,700,000,000
Deposits with banks	246,400,000,000		114,100,000,000
Accrued interest and accounts receivable	0		0
Federal funds sold and securities purchased under resale agreements (included $32,862 and $24,891 at fair value)	0		0
Securities borrowed	0		0
Loans, at fair value	0		0
Total other assets	0		0
Financial liabilities
Deposits	0		0
Federal funds purchased and securities loaned or sold under repurchase agreements (included $9.5 and $4.1 at fair value)	0		0
Commercial paper	0		0
Other Short-term Borrowings	0		0
Accounts payable and other liabilities	0		0
Beneficial interest liability, at fair value	0		0
Long-term debt and junior subordinated deferrable interest debentures	0		0
Wholesale lending related commitments	0		0
Estimate of Fair Value | Estimate of Fair Value, Level 2 Inputs [Member]
Financial assets
Cash and due from banks	0		0
Deposits with banks	11,200,000,000		7,700,000,000
Accrued interest and accounts receivable	73,800,000,000		60,300,000,000
Federal funds sold and securities purchased under resale agreements (included $32,862 and $24,891 at fair value)	192,700,000,000		272,000,000,000
Securities borrowed	108,600,000,000		108,800,000,000
Loans, at fair value	21,600,000,000		26,400,000,000
Total other assets	46,100,000,000		42,700,000,000
Financial liabilities
Deposits	1,195,700,000,000		1,187,200,000,000
Federal funds purchased and securities loaned or sold under repurchase agreements (included $9.5 and $4.1 at fair value)	243,900,000,000		235,700,000,000
Commercial paper	58,800,000,000		55,400,000,000
Other Short-term Borrowings	13,400,000,000		15,000,000,000
Accounts payable and other liabilities	159,100,000,000		153,800,000,000
Beneficial interest liability, at fair value	53,000,000,000		57,700,000,000
Long-term debt and junior subordinated deferrable interest debentures	239,200,000,000		220,000,000,000
Wholesale lending related commitments	0		0
Estimate of Fair Value | Estimate of Fair Value, Level 3 Inputs [Member]
Financial assets
Cash and due from banks	0		0
Deposits with banks	0		0
Accrued interest and accounts receivable	400,000,000		600,000,000
Federal funds sold and securities purchased under resale agreements (included $32,862 and $24,891 at fair value)	0		0
Securities borrowed	0		0
Loans, at fair value	685,900,000,000		685,400,000,000
Total other assets	5,300,000,000		7,400,000,000
Financial liabilities
Deposits	1,200,000,000		1,200,000,000
Federal funds purchased and securities loaned or sold under repurchase agreements (included $9.5 and $4.1 at fair value)	0		0
Commercial paper	0		0
Other Short-term Borrowings	0		0
Accounts payable and other liabilities	1,700,000,000		2,500,000,000
Beneficial interest liability, at fair value	4,300,000,000		4,400,000,000
Long-term debt and junior subordinated deferrable interest debentures	5,500,000,000		5,400,000,000
Wholesale lending related commitments	$ 1,400,000,000		$ 1,900,000,000