Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	$ 951		$ 1,076
Fair Value Measured On Nonrecurring Basis Gains Losses			(68)
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	951		1,076
Loans Held-for-Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	4	[1]	2	[1]
Fair Value Measured On Nonrecurring Basis Gains Losses	(4)	[1]	(1)	[1]
Loans Held-for-Sale | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	4	[1]	2	[1]
Commercial and Industrial Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	20		69
Fair Value Measured On Nonrecurring Basis Gains Losses	(6)		(30)
Commercial and Industrial Loans | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	20		69
Commercial Mortgage Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	34		81
Fair Value Measured On Nonrecurring Basis Gains Losses	(17)		(13)
Commercial Mortgage Loans | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	34		81
Commercial Construction
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	7		37
Fair Value Measured On Nonrecurring Basis Gains Losses			(12)
Commercial Construction | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	7		37
Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	766		767
Fair Value Measured On Nonrecurring Basis Gains Losses	49		11
Servicing Rights | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	766		767
Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	120		120
Fair Value Measured On Nonrecurring Basis Gains Losses	(22)		(23)
Other Real Estate Owned | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	$ 120		$ 120

[1]  Includes commercial nonaccrual loans held for sale