Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	$ 1,076		$ 1,276		$ 1,076		$ 1,276
Fair Value Measured On Nonrecurring Basis Gains Losses	(133)		(259)		(201)		(451)
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	1,076		1,276		1,076		1,276
Loans Held For Sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	8	[1]	17	[1]	8	[1]	17	[1]
Fair Value Measured On Nonrecurring Basis Gains Losses	(5)	[1]	(9)	[1]	(6)	[1]	(25)	[1]
Loans Held For Sale [Member] | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	8	[1]	17	[1]	8	[1]	17	[1]
Commercial And Industrial Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	77		115		77		115
Fair Value Measured On Nonrecurring Basis Gains Losses	(25)		(114)		(56)		(199)
Commercial And Industrial Loans [Member] | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	77		115		77		115
Commercial Mortgage Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	95		109		95		109
Fair Value Measured On Nonrecurring Basis Gains Losses	(16)		(22)		(29)		(53)
Commercial Mortgage Loans [Member] | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	95		109		95		109
Commercial Construction
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	26		35		26		35
Fair Value Measured On Nonrecurring Basis Gains Losses	(5)		(19)		(16)		(38)
Commercial Construction | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	26		35		26		35
Mortgage Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	736		847		736		847
Fair Value Measured On Nonrecurring Basis Gains Losses	(60)		(63)		(49)		(27)
Mortgage Servicing Rights | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	736		847		736		847
Other Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	134		153		134		153
Fair Value Measured On Nonrecurring Basis Gains Losses	(22)		(32)		(45)		(109)
Other Real Estate Owned [Member] | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	$ 134		$ 153		$ 134		$ 153

[1] Includes commercial nonaccrual loans held for sale