Goodwill and Other Intangible Assets - Changes in the Carrying Amounts of Other Intangible Assets (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Finite-Lived Intangible Assets, Net	$ 57
Amortization	(39)		(43)
Origination of Mortgage Servicing Rights (MSRs)	336		224		289
Due to changes in inputs or assumptions	(112)	[1]	(533)	[1]
Servicing Asset at Fair Value, Other Changes in Fair Value	(241)	[2]	(200)	[2]
Sale of MSRs	(5)		(9)
Other			(7)
Ending Balance	956		1,017		1,571
Core Deposits [Member]
Finite-Lived Intangible Assets, Net	17
Amortization	(21)		(29)
Origination of Mortgage Servicing Rights (MSRs)	0		0
Due to changes in inputs or assumptions	0		0
Servicing Asset at Fair Value, Other Changes in Fair Value	0		0
Sale of MSRs	0		0
Other			0
Ending Balance	17		38		67
Mortgage Servicing Rights, Fair Value [Member]
Amortization	0		0
Origination of Mortgage Servicing Rights (MSRs)	336		224
Due to changes in inputs or assumptions	(112)	[1]	(533)	[1]
Servicing Asset at Fair Value, Other Changes in Fair Value	(241)	[2]	(200)	[2]
Sale of MSRs	(5)		(9)
Other			0
Ending Balance	899		921		1,439
Other Intangible Assets [Member]
Finite-Lived Intangible Assets, Net	40
Amortization	(18)		(14)
Origination of Mortgage Servicing Rights (MSRs)	0		0
Due to changes in inputs or assumptions	0		0
Servicing Asset at Fair Value, Other Changes in Fair Value	0		0
Sale of MSRs	0		0
Other			(7)
Ending Balance	$ 40		$ 58		$ 65

[1] Primarily reflects changes in discount rates and prepayment speed assumptions, due to changes in interest rates.

[2] Represents changes due to the collection of expected cash flows, net of accretion, due to the passage of time.