Goodwill and Other Intangible Assets - Changes in the Carrying Amounts of Other Intangible Assets (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Dec. 31, 2013	Dec. 31, 2012
Servicing Asset at Fair Value, Amount	$ 1,305				$ 1,300
Amortization	(10)		(18)
Origination of Mortgage Servicing Rights (MSRs)	137		302
Servicing Assets at Fair Value, Purchased	109
Due to changes in inputs or assumptions	(117)	[1]	260	[1]
Servicing Asset at Fair Value, Other Changes in Fair Value	(123)	[2]	(212)	[2]
Servicing Asset at Fair Value, Disposals	(1)		(1)
Intangible Assets, Written off Related to Sale of Business Unit	(9)
Ending Balance	1,320		1,287		1,334	956
Mortgage Servicing Rights, Fair Value [Member]
Servicing Asset at Fair Value, Amount	1,305		1,248		1,300	899
Amortization	0		0
Origination of Mortgage Servicing Rights (MSRs)	137		302
Servicing Assets at Fair Value, Purchased	109
Due to changes in inputs or assumptions	(117)	[1]	260	[1]
Servicing Asset at Fair Value, Other Changes in Fair Value	(123)	[2]	(212)	[2]
Servicing Asset at Fair Value, Disposals	(1)		(1)
Intangible Assets, Written off Related to Sale of Business Unit	0
Other Intangible Assets [Member]
Amortization	(6)		(8)
Origination of Mortgage Servicing Rights (MSRs)			0
Servicing Assets at Fair Value, Purchased	0
Due to changes in inputs or assumptions	0		0
Servicing Asset at Fair Value, Other Changes in Fair Value	0		0
Servicing Asset at Fair Value, Disposals	0		0
Intangible Assets, Written off Related to Sale of Business Unit	(9)
Ending Balance	15		32		30	40
Core Deposits [Member]
Amortization	(4)		(10)
Origination of Mortgage Servicing Rights (MSRs)			0
Servicing Assets at Fair Value, Purchased	0
Due to changes in inputs or assumptions	0		0
Servicing Asset at Fair Value, Other Changes in Fair Value	0		0
Servicing Asset at Fair Value, Disposals	0		0
Intangible Assets, Written off Related to Sale of Business Unit	0
Ending Balance	$ 0		$ 7		$ 4	$ 17

[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.