Change in Fair Value of Financial Instruments for which the FVO has been Elected (Detail) - USD ($) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2015		Sep. 30, 2014
Mortgage Servicing Rights [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		$ 198	[1]	$ 55	[2]	$ 234	[1]	$ 238	[2]
Mortgage Servicing Rights [Member] | Other Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0				0
Mortgage Servicing Rights [Member] | Trading Revenue [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0		0		0		0
Mortgage Servicing Rights [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0		0		(1)		(2)
Mortgage Servicing Rights [Member] | Mortgage Servicing Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		198		55		235		240
Long-term Debt [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		(9)	[1]	(9)	[2]	(28)	[1]	(6)	[2]
Long-term Debt [Member] | Other Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0				0
Long-term Debt [Member] | Trading Revenue [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		(9)		(9)		(28)		(6)
Long-term Debt [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0		0		0		0
Long-term Debt [Member] | Mortgage Servicing Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0		0		0		0
Brokered Deposits [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	[2]			(1)				(6)
Brokered Deposits [Member] | Trading Revenue [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)				(1)				(6)
Brokered Deposits [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)				0				0
Brokered Deposits [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)		0	[2]	(3)	[1]	(8)	[2]
Loans Held For Investment [Member] | Other Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		(4)				(3)
Loans Held For Investment [Member] | Trading Revenue [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0		0		0		0
Loans Held For Investment [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0		0		0		(8)
Loans Held For Investment [Member] | Mortgage Servicing Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0		0		0		0
Loans Held For Sale [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		(20)	[1]	32	[2]	(32)	[1]	18	[2]
Loans Held For Sale [Member] | Other Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0				0
Loans Held For Sale [Member] | Trading Revenue [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0		0		0		0
Loans Held For Sale [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		(20)		32		(32)		18
Loans Held For Sale [Member] | Mortgage Servicing Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0		0		0		0
Trading Account Assets [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		1	[1]	(1)	[2]	(1)	[1]	(10)	[2]
Trading Account Assets [Member] | Other Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0				0
Trading Account Assets [Member] | Trading Revenue [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		1		(1)		(1)		(10)
Trading Account Assets [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0		0		0		0
Trading Account Assets [Member] | Mortgage Servicing Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		$ 0		$ 0		$ 0		$ 0

[1] Changes in fair value for the three and nine months ended September 30, 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 measured 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 and nine months ended September 30, 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 measured at fair value are recognized in interest income or interest expense in the Consolidated Statements of Income.