Estimated Fair Values of Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Financial Assets
Cash and due from banks	$ 9,382		$ 13,962
Investment securities held-to-maturity	34,509	[1]	18,877	[1]
Loans	213,669		205,082
Financial Liabilities
Deposits	244,232		230,885
Short-term borrowings	27,853		30,468
Long-term debt	26,264		31,953
Carrying Amount
Financial Assets
Cash and due from banks	9,382		13,962
Federal funds sold and securities purchased under resale agreements	166		64
Investment securities held-to-maturity	34,509		18,877
Mortgages held for sale			3	[2]
Other loans held for sale	64		228
Loans	213,669		205,082
Other financial instruments	6,991		6,095
Financial Liabilities
Deposits	244,232		230,885
Short-term borrowings	27,853		30,468
Long-term debt	26,264		31,953
Fair Value
Financial Assets
Cash and due from banks	9,382		13,962
Federal funds sold and securities purchased under resale agreements	166		64
Investment securities held-to-maturity	35,226		19,216
Mortgages held for sale			3	[2]
Other loans held for sale	64		228
Loans	216,105		206,646
Other financial instruments	7,017		6,140
Financial Liabilities
Deposits	244,690		231,184
Short-term borrowings	27,885		30,448
Long-term debt	27,264		32,664
Fair Value | Level 1
Financial Assets
Cash and due from banks	9,382
Investment securities held-to-maturity	2,441
Fair Value | Level 2
Financial Assets
Federal funds sold and securities purchased under resale agreements	166
Investment securities held-to-maturity	32,719
Other financial instruments	1,246
Financial Liabilities
Deposits	244,690
Short-term borrowings	27,885
Long-term debt	27,264
Fair Value | Level 3
Financial Assets
Investment securities held-to-maturity	66
Other loans held for sale	64
Loans	216,105
Other financial instruments	$ 5,771

[1] Includes only collateral pledged by the Company where counterparties have the right to sell or pledge the collateral.

[2] Balance excludes mortgages held for sale for which the fair value option under applicable accounting guidance was elected.