Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	$ 1,134	$ 1,076	$ 1,134	$ 1,076
Fair Value Measured On Nonrecurring Basis Gains Losses	59	(133)	59	(201)
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	1,134	1,076	1,134	1,076
Loans Held-for-Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	2	8	2	8
Fair Value Measured On Nonrecurring Basis Gains Losses	(1)	(5)	(5)	(6)
Loans Held-for-Sale | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	2	8	2	8
Commercial and Industrial Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	83	77	83	77
Fair Value Measured On Nonrecurring Basis Gains Losses	(25)	(25)	(31)	(56)
Commercial and Industrial Loans | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	83	77	83	77
Commercial Mortgage Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	35	95	35	95
Fair Value Measured On Nonrecurring Basis Gains Losses	(8)	(16)	(25)	(29)
Commercial Mortgage Loans | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	35	95	35	95
Commercial Construction
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	8	26	8	26
Fair Value Measured On Nonrecurring Basis Gains Losses	(2)	(5)	(2)	(16)
Commercial Construction | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	8	26	8	26
Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	894	736	894	736
Fair Value Measured On Nonrecurring Basis Gains Losses	102	(60)	151	(49)
Servicing Rights | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	894	736	894	736
Other Real Estate Owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	112	134	112	134
Fair Value Measured On Nonrecurring Basis Gains Losses	(7)	(22)	(29)	(45)
Other Real Estate Owned | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair Value Measurements	$ 112	$ 134	$ 112	$ 134