Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	$ 1,161	$ 1,342
Fair Value Measured On Nonrecurring Basis Gains Losses	(128)	(142)
Commercial Loans Held-for-Sale | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	5	1
Fair Value Measured On Nonrecurring Basis Gains Losses	(2)	4
Commercial and Industrial Loans | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	347	366
Fair Value Measured On Nonrecurring Basis Gains Losses	(47)	(43)
Commercial Mortgage Loans | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	85	52
Fair Value Measured On Nonrecurring Basis Gains Losses	6	(13)
Commercial Construction Loans | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measured On Nonrecurring Basis Gains Losses	2
Residential mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements		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	685	788
Fair Value Measured On Nonrecurring Basis Gains Losses	(85)	(48)
Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	27	36
Fair Value Measured On Nonrecurring Basis Gains Losses	(3)	(8)
Bank premises and equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	12	5
Fair Value Measured On Nonrecurring Basis Gains Losses	1	(3)
Operating lease equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements		39
Fair Value Measured On Nonrecurring Basis Gains Losses		(30)
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	1,161	1,342
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	5	1
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	347	366
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	85	52
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
Fair Value, Inputs, Level 3 | Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements	685	788
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	27	36
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	$ 12	5
Fair Value, Inputs, Level 3 | Operating lease equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurements		$ 39