Fair Value (Carrying Value and Estimated Fair Value of Financial Instruments) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Financial Assets:
Cash and due from banks	$ 6,247	$ 3,220	$ 5,479	$ 2,590
Interest-bearing deposits with banks	98,386	64,257
Securities purchased under resale agreements	3,681	6,230
Investment securities held to maturity	18,757	17,740
Financial Liabilities:
Noninterest-bearing	73,109	65,614
Interest-bearing—U.S.	27,584	13,392
Interest-bearing—non-U.S.	118,141	103,262
Securities sold under repurchase agreements	9,168	7,953
Federal funds purchased	14	19
Other short-term borrowings	4,322	3,780
Long-term debt	9,037	9,699
Estimated Fair Value
Financial Assets:
Cash and due from banks	6,247	3,220
Interest-bearing deposits with banks	98,386	64,257
Securities purchased under resale agreements	3,681	6,230
Investment securities held to maturity	18,864	17,560
Net loans (excluding leases)	15,709	12,355
Financial Liabilities:
Noninterest-bearing	73,109	65,614
Interest-bearing—U.S.	27,584	13,392
Interest-bearing—non-U.S.	118,141	103,262
Securities sold under repurchase agreements	9,168	7,953
Federal funds purchased	14	19
Other short-term borrowings	4,322	3,780
Long-term debt	9,412	9,909
Reported Amount
Financial Assets:
Cash and due from banks	6,247	3,220
Interest-bearing deposits with banks	98,386	64,257
Securities purchased under resale agreements	3,681	6,230
Investment securities held to maturity	18,757	17,740
Net loans (excluding leases)	15,695	12,363
Financial Liabilities:
Noninterest-bearing	73,109	65,614
Interest-bearing—U.S.	27,584	13,392
Interest-bearing—non-U.S.	118,141	103,262
Securities sold under repurchase agreements	9,168	7,953
Federal funds purchased	14	19
Other short-term borrowings	4,322	3,780
Long-term debt	9,037	9,699
Quoted Market Prices in Active Markets (Level 1) | Estimated Fair Value
Financial Assets:
Cash and due from banks	6,247	3,220
Interest-bearing deposits with banks	0	0
Securities purchased under resale agreements	0	0
Investment securities held to maturity	0	0
Net loans (excluding leases)	0	0
Financial Liabilities:
Noninterest-bearing	0	0
Interest-bearing—U.S.	0	0
Interest-bearing—non-U.S.	0	0
Securities sold under repurchase agreements	0	0
Federal funds purchased	0	0
Other short-term borrowings	0	0
Long-term debt	0	0
Pricing Methods with Significant Observable Market Inputs (Level 2) | Estimated Fair Value
Financial Assets:
Cash and due from banks	0	0
Interest-bearing deposits with banks	98,386	64,257
Securities purchased under resale agreements	3,681	6,230
Investment securities held to maturity	18,864	17,560
Net loans (excluding leases)	15,223	11,908
Financial Liabilities:
Noninterest-bearing	73,109	65,614
Interest-bearing—U.S.	27,584	13,392
Interest-bearing—non-U.S.	118,141	103,262
Securities sold under repurchase agreements	9,168	7,953
Federal funds purchased	14	19
Other short-term borrowings	4,322	3,780
Long-term debt	8,525	9,056
Pricing Methods with Significant Unobservable Market Inputs (Level 3) | Estimated Fair Value
Financial Assets:
Cash and due from banks	0	0
Interest-bearing deposits with banks	0	0
Securities purchased under resale agreements	0	0
Investment securities held to maturity	0	0
Net loans (excluding leases)	486	447
Financial Liabilities:
Noninterest-bearing	0	0
Interest-bearing—U.S.	0	0
Interest-bearing—non-U.S.	0	0
Securities sold under repurchase agreements	0	0
Federal funds purchased	0	0
Other short-term borrowings	0	0
Long-term debt	$ 887	$ 853