Change in Fair Value of Financial Instruments for which the FVO has been Elected (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended					3 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012	Mar. 31, 2014	Sep. 30, 2013
Deposits [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	$ 6	[1]	$ 8	[2]
Deposits [Member] | Trading Account Profits And Commissions [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	6		8
Deposits [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	0		0
Deposits [Member] | Mortgage Servicing Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	0		0
Trading Account Assets [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	11	[1]	13	[2]
Trading Account Assets [Member] | Trading Account Profits And Commissions [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	11		13
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)	3	[1]	(134)	[2]
Loans Held For Sale [Member] | Trading Account Profits And Commissions [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	0		1
Loans Held For Sale [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	3	[3]	(135)	[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)	11	[1]	(10)	[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)	11	[3]	(10)	[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)	(398)	[1]	54	[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)	3	[3]	4	[4]
Mortgage Servicing Rights [Member] | Mortgage Servicing Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	(401)		50
Long-term Debt [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	17	[1]	36	[2]
Long-term Debt [Member] | Trading Account Profits And Commissions [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	17		36
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
Brokered Deposits [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					5
Mortgage Servicing Rights [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					(322)
Loans Held For Investment [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					21
Loans Held For Sale [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					171
Trading Account Assets [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					8
Long-term Debt [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					(65)
Mortgage Production Income [Member] | Brokered Deposits [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					0
Mortgage Production Income [Member] | Mortgage Servicing Rights [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					31
Mortgage Production Income [Member] | Loans Held For Investment [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					20
Mortgage Production Income [Member] | Loans Held For Sale [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					161
Mortgage Production Income [Member] | Trading Account Assets [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					0
Mortgage Production Income [Member] | Long-term Debt [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					0
Mortgage Servicing Income [Member] | Brokered Deposits [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					0
Mortgage Servicing Income [Member] | Mortgage Servicing Rights [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					(353)
Mortgage Servicing Income [Member] | Loans Held For Investment [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					0
Mortgage Servicing Income [Member] | Loans Held For Sale [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					0
Mortgage Servicing Income [Member] | Trading Account Assets [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					0
Mortgage Servicing Income [Member] | Long-term Debt [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					0
Trading Account Profits And Commissions [Member] | Brokered Deposits [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					5
Trading Account Profits And Commissions [Member] | Mortgage Servicing Rights [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					0
Trading Account Profits And Commissions [Member] | Loans Held For Investment [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					1
Trading Account Profits And Commissions [Member] | Loans Held For Sale [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					10
Trading Account Profits And Commissions [Member] | Trading Account Assets [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					8
Trading Account Profits And Commissions [Member] | Long-term Debt [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)					(65)
Affordable Housing [Member]
Asset Impairment Charges	(15)
Fair Value, Measurements, Nonrecurring [Member] | Affordable Housing [Member]
Asset Impairment Charges	21		3			36	9
Fair Value, Measurements, Nonrecurring [Member] | Other Assets [Member]
Asset Impairment Charges	64		61
Property Subject to Operating Lease [Member] | Fair Value, Measurements, Nonrecurring [Member] | Other Assets [Member]
Asset Impairment Charges	59		50
Land [Member] | Fair Value, Measurements, Nonrecurring [Member] | Other Assets [Member]
Asset Impairment Charges	$ 5		$ 0

[1] Changes in fair value for the year ended December 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 year ended December 31, 2013 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.

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

[4] 1 Income related to LHFS does not include income from IRLCs. For the year ended December 31, 2013, income related to MSRs includes mortgage servicing income recognized upon the sale of loans reported at LOCOM.