Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	$ 2,144		$ 1,766
Fair Value Measured On Nonrecurring Basis Gains (Losses)	(629)		(202)
Commercial loans held for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	33	[1]	3	[1]
Fair Value Measured On Nonrecurring Basis Gains (Losses)	(12)	[1]	(7)	[1]
Residential Mortgagel Loans Held For Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	554
Fair Value Measured On Nonrecurring Basis Gains (Losses)	(87)
Commercial and Industrial Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	456		443
Fair Value Measured On Nonrecurring Basis Gains (Losses)	(382)		(281)
Commercial Mortgage Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	110		61
Fair Value Measured On Nonrecurring Basis Gains (Losses)	(36)		(41)
Commercial Construction
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	23		16
Fair Value Measured On Nonrecurring Basis Gains (Losses)	(1)		(10)
Mortgage Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	856		967
Fair Value Measured On Nonrecurring Basis Gains (Losses)	(65)		192
Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	90		87
Fair Value Measured On Nonrecurring Basis Gains (Losses)	(26)		(45)
Bank premises
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	22		8
Fair Value Measured On Nonrecurring Basis Gains (Losses)	(20)		(6)
Private equity investment funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements			181
Fair Value Measured On Nonrecurring Basis Gains (Losses)			(4)
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	2,144		1,766
Fair Value, Inputs, Level 3 | Commercial loans held for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	33	[1]	3	[1]
Fair Value, Inputs, Level 3 | Residential Mortgagel Loans Held For Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	554
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	456		443
Fair Value, Inputs, Level 3 | Commercial Mortgage Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	110		61
Fair Value, Inputs, Level 3 | Commercial Construction
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	23		16
Fair Value, Inputs, Level 3 | Mortgage Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	856		967
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	90		87
Fair Value, Inputs, Level 3 | Bank premises
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	22		8
Fair Value, Inputs, Level 3 | Private equity investment funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements			$ 181

[1] Includes commercial nonaccrual loans held for sale.