Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	$ 1,346	$ 1,575
Fair Value Measured On Nonrecurring Basis Gains (Losses)	(262)	(340)
Commercial loans held for sale | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	5	13
Fair Value Measured On Nonrecurring Basis Gains (Losses)	(32)	3
Residential Mortgagel Loans Held For Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements		68
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
Fair Value Measurements		2
Fair Value Measured On Nonrecurring Basis Gains (Losses)		0
Credit Card Held For Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements		4
Fair Value Measured On Nonrecurring Basis Gains (Losses)		(2)
Commercial and Industrial Loans | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	412	344
Fair Value Measured On Nonrecurring Basis Gains (Losses)	(166)	(137)
Commercial Mortgage Loans | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	15	103
Fair Value Measured On Nonrecurring Basis Gains (Losses)	(4)	(41)
Commercial Construction Loans | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	0	6
Fair Value Measured On Nonrecurring Basis Gains (Losses)	2	(5)
Commercial Leases | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	3
Fair Value Measured On Nonrecurring Basis Gains (Losses)	(3)
Residential mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
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
Fair Value Measurements	744	784
Fair Value Measured On Nonrecurring Basis Gains (Losses)	7	4
Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	42	58
Fair Value Measured On Nonrecurring Basis Gains (Losses)	(17)	(24)
Bank premises and equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	28	83
Fair Value Measured On Nonrecurring Basis Gains (Losses)	(31)	(101)
Operating lease equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	37	42
Fair Value Measured On Nonrecurring Basis Gains (Losses)	(9)	(33)
Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	60	13
Fair Value Measured On Nonrecurring Basis Gains (Losses)	(9)	(1)
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	1,346	1,575
Fair Value, Inputs, Level 3 | Commercial loans held for sale | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	5	13
Fair Value, Inputs, Level 3 | Residential Mortgagel Loans Held For Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements		68
Fair Value, Inputs, Level 3 | Automobile Loans Held For Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements		2
Fair Value, Inputs, Level 3 | Credit Card Held For Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements		4
Fair Value, Inputs, Level 3 | Commercial and Industrial Loans | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	412	344
Fair Value, Inputs, Level 3 | Commercial Mortgage Loans | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	15	103
Fair Value, Inputs, Level 3 | Commercial Construction Loans | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	0	6
Fair Value, Inputs, Level 3 | Commercial Leases | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	3
Fair Value, Inputs, Level 3 | Residential mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements		55
Fair Value, Inputs, Level 3 | Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	744	784
Fair Value, Inputs, Level 3 | Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	42	58
Fair Value, Inputs, Level 3 | Bank premises and equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	28	83
Fair Value, Inputs, Level 3 | Operating lease equipment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	37	42
Fair Value, Inputs, Level 3 | Private equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	$ 60	$ 13