Goodwill and Other Intangible Assets - Changes in the Carrying Amounts of Other Intangible Assets (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2014	Dec. 31, 2013
Amortization of Intangible Assets and Impairment of Goodwill	$ 7		$ 3
Servicing Asset at Fair Value, Amount	1,181				1,206
Amortization	(1)	[1]	(3)	[1]
Origination of Mortgage Servicing Rights (MSRs)	46		32
Servicing Assets at Fair Value, Purchased	56
Due to changes in inputs or assumptions	(78)	[2]	(46)	[2]
Servicing Asset at Fair Value, Other Changes in Fair Value	(48)	[3]	(35)	[3]
Servicing Asset at Fair Value, Disposals	(1)
Ending Balance	1,193		1,282		1,219	1,334
Mortgage Servicing Rights, Fair Value [Member]
Servicing Asset at Fair Value, Amount	1,181		1,251		1,206	1,300
Amortization	0		0
Origination of Mortgage Servicing Rights (MSRs)	46		32
Servicing Assets at Fair Value, Purchased	56
Due to changes in inputs or assumptions	(78)	[1]	(46)	[2]
Servicing Asset at Fair Value, Other Changes in Fair Value	(48)	[3]	(35)	[3]
Servicing Asset at Fair Value, Disposals	(1)
Other Intangible Assets [Member]
Amortization	(1)	[1]	(3)	[1]
Origination of Mortgage Servicing Rights (MSRs)	0		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
Ending Balance	12		31		13	34
Community Development Investments [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Amortization of Intangible Assets and Impairment of Goodwill	$ 6		$ 3

[1] Amortization of tax credits for non-qualified community development investments totaled $6 million reflected in amortization expense and $3 million reflected in other noninterest expense in the Company's Consolidated Statements of Income for the three months ended March 31, 2015 and 2014, respectively. See Note 8, "Certain Transfers of Financial Assets and Variable Interest Entities," for additional information.

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

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