Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	$ 1,534	$ 1,479	$ 1,534	$ 1,479
Fair Value Measured On Nonrecurring Basis Gains Losses	(162)	(130)	(329)	(338)
Commercial Loans Held-for-Sale | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	14	25	14	25
Fair Value Measured On Nonrecurring Basis Gains Losses		(5)	3	(7)
Residential Mortgagel Loans Held For Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	96		96
Fair Value Measured On Nonrecurring Basis Gains Losses			(2)
Automobile Loans Held For Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	2		2
Credit Card Held For Sale
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	(1)		(1)
Commercial and Industrial Loans | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	290	387	290	387
Fair Value Measured On Nonrecurring Basis Gains Losses	(57)	(135)	(98)	(259)
Commercial Mortgage Loans | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	112	49	112	49
Fair Value Measured On Nonrecurring Basis Gains Losses	(19)	(8)	(36)	(25)
Commercial Construction Loans | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	9	4	9	4
Fair Value Measured On Nonrecurring Basis Gains Losses	(2)		(2)
Residential mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	55		55
Fair Value Measured On Nonrecurring Basis Gains Losses			(1)
Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	756	933	756	933
Fair Value Measured On Nonrecurring Basis Gains Losses	(77)	21	(38)	(7)
Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	64	77	64	77
Fair Value Measured On Nonrecurring Basis Gains Losses	(3)	(3)	(16)	(22)
Bank premises and equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	79	4	79	4
Fair Value Measured On Nonrecurring Basis Gains Losses	(1)		(102)	(18)
Operating lease equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	53		53
Fair Value Measured On Nonrecurring Basis Gains Losses	(2)		(36)
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	1,534	1,479	1,534	1,479
Fair Value, Inputs, Level 3 | Commercial Loans Held-for-Sale | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	14	25	14	25
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	96		96
Fair Value, Inputs, Level 3 | Automobile Loans Held For Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	2		2
Fair Value, Inputs, Level 3 | Credit Card Held For Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	4		4
Fair Value, Inputs, Level 3 | Commercial and Industrial Loans | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	290	387	290	387
Fair Value, Inputs, Level 3 | Commercial Mortgage Loans | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	112	49	112	49
Fair Value, Inputs, Level 3 | Commercial Construction Loans | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	9	4	9	4
Fair Value, Inputs, Level 3 | Residential mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	55		55
Fair Value, Inputs, Level 3 | Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	756	933	756	933
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	64	77	64	77
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	79	$ 4	79	$ 4
Fair Value, Inputs, Level 3 | Operating lease equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	$ 53		$ 53