Fair Value Measurement - Carrying Value and Estimated Fair Value (Details 7) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Financial assets
Cash and due from banks	$ 29,214,000,000	$ 44,866,000,000	$ 29,214,000,000	$ 44,866,000,000	$ 53,723,000,000	$ 59,602,000,000
Deposits with banks	311,318,000,000		311,318,000,000		121,814,000,000
Federal funds sold and securities purchased under resale agreements (included $25,306 and $24,258 at fair value)	252,507,000,000		252,507,000,000		296,296,000,000
Financial liabilities
Commercial paper	56,631,000,000		56,631,000,000		55,367,000,000
Other Short-term Borrowings	30,385,000,000		30,385,000,000		26,636,000,000
Beneficial interest liability, at fair value	55,090,000,000		55,090,000,000		63,191,000,000
Trading assets and liabilities average balances Abstract
Trading assets - debt and equity instruments	357,285,000,000	346,708,000,000	363,952,000,000	351,021,000,000
Trading assets - derivative receivables	75,310,000,000	89,345,000,000	75,115,000,000	89,896,000,000
Trading liabilities - debt and equity instruments	75,671,000,000	69,763,000,000	73,103,000,000	69,374,000,000
Trading liabilities - derivative payables	66,246,000,000	78,704,000,000	67,458,000,000	77,387,000,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Financial assets
Securities borrowed	0		0		0
Loans, at fair value	1,843,000,000		1,843,000,000		2,282,000,000
Financial liabilities
Deposits	2,190,000,000		2,190,000,000		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		0
Other Short-term Borrowings	2,673,000,000		2,673,000,000		1,619,000,000
Accounts payable and other liabilities	32,000,000		32,000,000		36,000,000
Long-term debt and junior subordinated deferrable interest debentures	9,202,000,000		9,202,000,000		8,476,000,000
Fair value | Fair Value, Measurements, Recurring [Member]
Financial assets
Securities borrowed	5,295,000,000		5,295,000,000		10,177,000,000
Loans, at fair value	1,923,000,000		1,923,000,000		2,555,000,000
Financial liabilities
Deposits	5,838,000,000		5,838,000,000		5,733,000,000
Federal funds purchased and securities loaned or sold under repurchase agreements (included $9.5 and $4.1 at fair value)	4,661,000,000		4,661,000,000		4,388,000,000
Other Short-term Borrowings	12,572,000,000		12,572,000,000		11,591,000,000
Accounts payable and other liabilities	32,000,000		32,000,000		36,000,000
Long-term debt and junior subordinated deferrable interest debentures	29,220,000,000		29,220,000,000		30,788,000,000
Carrying value
Financial assets
Cash and due from banks	29,200,000,000		29,200,000,000		53,700,000,000
Deposits with banks	311,300,000,000		311,300,000,000		121,800,000,000
Accrued interest and accounts receivable	81,600,000,000		81,600,000,000		60,900,000,000
Federal funds sold and securities purchased under resale agreements (included $25,306 and $24,258 at fair value)	227,200,000,000		227,200,000,000		272,000,000,000
Securities borrowed	111,900,000,000		111,900,000,000		108,800,000,000
Loans, at fair value	704,300,000,000		704,300,000,000		709,300,000,000
Total other assets	57,200,000,000		57,200,000,000		49,700,000,000
Financial liabilities
Deposits	1,197,100,000,000		1,197,100,000,000		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)	254,300,000,000		254,300,000,000		235,700,000,000
Commercial paper	56,600,000,000		56,600,000,000		55,400,000,000
Other Short-term Borrowings	17,800,000,000		17,800,000,000		15,000,000,000
Accounts payable and other liabilities	178,000,000,000		178,000,000,000		156,500,000,000
Beneficial interest liability, at fair value	54,000,000,000		54,000,000,000		62,000,000,000
Long-term debt and junior subordinated deferrable interest debentures	237,000,000,000		237,000,000,000		218,200,000,000
Wholesale lending related commitments	700,000,000		700,000,000		700,000,000
Estimate of Fair Value
Financial assets
Cash and due from banks	29,200,000,000		29,200,000,000		53,700,000,000
Deposits with banks	311,300,000,000		311,300,000,000		121,800,000,000
Accrued interest and accounts receivable	81,600,000,000		81,600,000,000		60,900,000,000
Federal funds sold and securities purchased under resale agreements (included $25,306 and $24,258 at fair value)	227,200,000,000		227,200,000,000		272,000,000,000
Securities borrowed	111,900,000,000		111,900,000,000		108,800,000,000
Loans, at fair value	706,300,000,000		706,300,000,000		711,800,000,000
Total other assets	57,800,000,000		57,800,000,000		50,100,000,000
Financial liabilities
Deposits	1,197,400,000,000		1,197,400,000,000		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)	254,300,000,000		254,300,000,000		235,700,000,000
Commercial paper	56,600,000,000		56,600,000,000		55,400,000,000
Other Short-term Borrowings	17,800,000,000		17,800,000,000		15,000,000,000
Accounts payable and other liabilities	178,100,000,000		178,100,000,000		156,300,000,000
Beneficial interest liability, at fair value	53,900,000,000		53,900,000,000		62,100,000,000
Long-term debt and junior subordinated deferrable interest debentures	243,700,000,000		243,700,000,000		225,400,000,000
Wholesale lending related commitments	1,400,000,000		1,400,000,000		1,900,000,000
Estimate of Fair Value | EstimateOfFairValueLevel1Inputs [Member]
Financial assets
Cash and due from banks	29,200,000,000		29,200,000,000		53,700,000,000
Deposits with banks	303,900,000,000		303,900,000,000		114,100,000,000
Accrued interest and accounts receivable	0		0		0
Federal funds sold and securities purchased under resale agreements (included $25,306 and $24,258 at fair value)	0		0		0
Securities borrowed	0		0		0
Loans, at fair value	0		0		0
Total other assets	0		0		0
Financial liabilities
Deposits	0		0		0
Federal funds purchased and securities loaned or sold under repurchase agreements (included $9.5 and $4.1 at fair value)	0		0		0
Commercial paper	0		0		0
Other Short-term Borrowings	0		0		0
Accounts payable and other liabilities	0		0		0
Beneficial interest liability, at fair value	0		0		0
Long-term debt and junior subordinated deferrable interest debentures	0		0		0
Wholesale lending related commitments	0		0		0
Estimate of Fair Value | Estimate of Fair Value, Level 2 Inputs [Member]
Financial assets
Cash and due from banks	0		0		0
Deposits with banks	7,400,000,000		7,400,000,000		7,700,000,000
Accrued interest and accounts receivable	81,300,000,000		81,300,000,000		60,300,000,000
Federal funds sold and securities purchased under resale agreements (included $25,306 and $24,258 at fair value)	227,200,000,000		227,200,000,000		272,000,000,000
Securities borrowed	111,900,000,000		111,900,000,000		108,800,000,000
Loans, at fair value	19,500,000,000		19,500,000,000		26,400,000,000
Total other assets	53,100,000,000		53,100,000,000		42,700,000,000
Financial liabilities
Deposits	1,196,200,000,000		1,196,200,000,000		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)	254,300,000,000		254,300,000,000		235,700,000,000
Commercial paper	56,600,000,000		56,600,000,000		55,400,000,000
Other Short-term Borrowings	17,800,000,000		17,800,000,000		15,000,000,000
Accounts payable and other liabilities	176,400,000,000		176,400,000,000		153,800,000,000
Beneficial interest liability, at fair value	49,900,000,000		49,900,000,000		57,700,000,000
Long-term debt and junior subordinated deferrable interest debentures	238,200,000,000		238,200,000,000		220,000,000,000
Wholesale lending related commitments	0		0		0
Estimate of Fair Value | Estimate of Fair Value, Level 3 Inputs [Member]
Financial assets
Cash and due from banks	0		0		0
Deposits with banks	0		0		0
Accrued interest and accounts receivable	300,000,000		300,000,000		600,000,000
Federal funds sold and securities purchased under resale agreements (included $25,306 and $24,258 at fair value)	0		0		0
Securities borrowed	0		0		0
Loans, at fair value	686,800,000,000		686,800,000,000		685,400,000,000
Total other assets	4,700,000,000		4,700,000,000		7,400,000,000
Financial liabilities
Deposits	1,200,000,000		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		0
Commercial paper	0		0		0
Other Short-term Borrowings	0		0		0
Accounts payable and other liabilities	1,700,000,000		1,700,000,000		2,500,000,000
Beneficial interest liability, at fair value	4,000,000,000		4,000,000,000		4,400,000,000
Long-term debt and junior subordinated deferrable interest debentures	5,500,000,000		5,500,000,000		5,400,000,000
Wholesale lending related commitments	$ 1,400,000,000		$ 1,400,000,000		$ 1,900,000,000