Change in Fair Value of Financial Instruments for which the FVO has been Elected (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				12 Months Ended
	Mar. 31, 2014		Mar. 31, 2015		Dec. 31, 2014
Deposits [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	$ 3	[1]
Deposits [Member] | Trading Account Profits And Commissions [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	3
Deposits [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	0
Deposits [Member] | Mortgage Servicing Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	0
Trading Account Assets [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	6	[1]	4	[2]
Trading Account Assets [Member] | Trading Account Profits And Commissions [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	6		4
Trading Account Assets [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	0		0
Trading Account Assets [Member] | Mortgage Servicing Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	0		0
Loans Held For Sale [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	(1)	[1]	12	[2]
Loans Held For Sale [Member] | Trading Account Profits And Commissions [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	0		0
Loans Held For Sale [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	(1)	[3]	12	[4]
Loans Held For Sale [Member] | Mortgage Servicing Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	0		0
Loans Held For Investment [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	4	[1]	2	[2]
Loans Held For Investment [Member] | Trading Account Profits And Commissions [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	0		0
Loans Held For Investment [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	4	[3]	2	[4]
Loans Held For Investment [Member] | Mortgage Servicing Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	0		0
Mortgage Servicing Rights [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	(81)	[1]	(125)	[2]
Mortgage Servicing Rights [Member] | Trading Account Profits And Commissions [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	0		0
Mortgage Servicing Rights [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	0	[3]	1	[4]
Mortgage Servicing Rights [Member] | Mortgage Servicing Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	(81)		(126)
Long-term Debt [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	(8)	[1]	1	[2]
Long-term Debt [Member] | Trading Account Profits And Commissions [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	(8)		1
Long-term Debt [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	0		0
Long-term Debt [Member] | Mortgage Servicing Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	0		0
Affordable Housing [Member]
Asset Impairment Charges					(15)
Fair Value, Measurements, Nonrecurring [Member] | Affordable Housing [Member]
Asset Impairment Charges	36				21
Fair Value, Measurements, Nonrecurring [Member] | Other Assets [Member]
Asset Impairment Charges			0		64
Property Subject to Operating Lease [Member] | Fair Value, Measurements, Nonrecurring [Member] | Other Assets [Member]
Asset Impairment Charges					59
Land [Member] | Fair Value, Measurements, Nonrecurring [Member] | Other Assets [Member]
Asset Impairment Charges			$ 0		$ 5

[1] Changes in fair value for the three months ended March 31, 2014 exclude accrued interest for the period then ended. Interest income or interest expense on trading loans, LHFS, LHFI, brokered time deposits, and long-term debt that have been elected to be carried at fair value are recognized in interest income or interest expense in the Consolidated Statements of Income.

[2] Changes in fair value for the three months ended March 31, 2015 exclude accrued interest for the period then ended. Interest income or interest expense on trading loans, LHFS, LHFI, and long-term debt that have been elected to be carried at fair value are recognized in interest income or interest expense in the Consolidated Statements of Income.

[3] 1 Income related to LHFS does not include income from IRLCs. For the three months ended March 31, 2014, income related to MSRs includes mortgage servicing income recognized upon the sale of loans reported at LOCOM.

[4] Income related to LHFS does not include income from IRLCs. For the three months ended March 31, 2015, income related to MSRs includes mortgage servicing income recognized upon the sale of loans reported at LOCOM.