Change in Fair Value of Financial Instruments for which the FVO has been Elected (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Trading Loans [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		$ (21)	[1]	$ (15)	[2]	$ 1	[3]
Trading Loans [Member] | Trading Revenue [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		(21)		(15)		1
Trading Loans [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0	[4]	0	[5]	0	[6]
Trading Loans [Member] | Mortgage Servicing Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0		0		0
Trading Loans [Member] | Other Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0		0		0
Loans Held For Sale [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		(61)	[1]	(75)	[2]	(44)	[3]
Loans Held For Sale [Member] | Trading Revenue [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0		0		0
Loans Held For Sale [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		(61)	[4]	(75)	[5]	(44)	[6]
Loans Held For Sale [Member] | Mortgage Servicing Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0		0		0
Loans Held For Sale [Member] | Other Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0		0		0
Loans Held For Investment [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	[3]					(5)
Loans Held For Investment [Member] | Trading Revenue [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)						0
Loans Held For Investment [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	[6]					0
Loans Held For Investment [Member] | Mortgage Servicing Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)						0
Loans Held For Investment [Member] | Other Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)						(5)
Mortgage Servicing Rights [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		243	[1]	242	[2]	240	[3]
Mortgage Servicing Rights [Member] | Trading Revenue [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0		0		0
Mortgage Servicing Rights [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		(5)	[4]	(3)	[5]	(2)	[6]
Mortgage Servicing Rights [Member] | Mortgage Servicing Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		248		245		242
Mortgage Servicing Rights [Member] | Other Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0		0		0
Brokered Time Deposits [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	[2]			(4)
Brokered Time Deposits [Member] | Trading Revenue [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)				(4)
Brokered Time Deposits [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	[5]			0
Brokered Time Deposits [Member] | Mortgage Servicing Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)				0
Brokered Time Deposits [Member] | Other Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)				0
Long-term Debt [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		(21)	[1]	(27)	[2]	(41)	[3]
Long-term Debt [Member] | Trading Revenue [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		(21)		(27)		(41)
Long-term Debt [Member] | Mortgage Production Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0	[4]	0	[5]	0	[6]
Long-term Debt [Member] | Mortgage Servicing Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		0		0		0
Long-term Debt [Member] | Other Income [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)		$ 0		$ 0		$ 0

[1] Changes in fair value for the year ended December 31, 2017 exclude accrued interest for the period then ended. Interest income or interest expense on trading loans, LHFS, 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 year ended December 31, 2016 exclude accrued interest for the period then ended. Interest income or interest expense on trading loans, LHFS, 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.

[3] Changes in fair value for the year ended December 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 measured at fair value are recognized in Interest income or Interest expense in the Consolidated Statements of Income.

[4] Income related to LHFS does not include income from IRLCs. For the year ended December 31, 2017, income related to residential MSRs includes income recognized upon the sale of loans reported at LOCOM.

[5] Income related to LHFS does not include income from IRLCs. For the year ended December 31, 2016, income related to residential MSRs includes income recognized upon the sale of loans reported at LOCOM.

[6] Income related to LHFS does not include income from IRLCs. For the year ended December 31, 2015, income related to residential MSRs includes income recognized upon the sale of loans reported at LOCOM.