Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013	Sep. 30, 2014		Sep. 30, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	$ 1,479		$ 1,522	$ 1,479		$ 1,522
Fair Value Measured On Nonrecurring Basis Gains Losses	(130)		(125)	(338)		(66)
Loans Held-for-Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	25	[1]		25	[1]
Fair Value Measured On Nonrecurring Basis Gains Losses	(5)	[1]		(7)	[1]	(5)	[1]
Commercial and Industrial Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	387		431	387		431
Fair Value Measured On Nonrecurring Basis Gains Losses	(135)		(103)	(259)		(134)
Commercial Mortgage Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	49		63	49		63
Fair Value Measured On Nonrecurring Basis Gains Losses	(8)		(9)	(25)		(34)
Commercial Construction
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	4		3	4		3
Fair Value Measured On Nonrecurring Basis Gains Losses			(4)			(6)
Commercial Leases
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements			1			1
Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	933		915	933		915
Fair Value Measured On Nonrecurring Basis Gains Losses	21		(1)	(7)		150
Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	77		109	77		109
Fair Value Measured On Nonrecurring Basis Gains Losses	(3)		(8)	(22)		(37)
Bank premises and equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	4			4
Fair Value Measured On Nonrecurring Basis Gains Losses				(18)
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	1,479		1,522	1,479		1,522
Fair Value, Inputs, Level 3 | Loans Held-for-Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	25	[1]		25	[1]
Fair Value, Inputs, Level 3 | Commercial and Industrial Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	387		431	387		431
Fair Value, Inputs, Level 3 | Commercial Mortgage Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	49		63	49		63
Fair Value, Inputs, Level 3 | Commercial Construction
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	4		3	4		3
Fair Value, Inputs, Level 3 | Commercial Leases
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements			1			1
Fair Value, Inputs, Level 3 | Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	933		915	933		915
Fair Value, Inputs, Level 3 | Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	77		109	77		109
Fair Value, Inputs, Level 3 | Bank premises and equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	$ 4			$ 4

[1]  Includes commercial nonaccrual loans held for sale