Reconciliation of the Beginning and Ending Balances for Fair Valued Assets and Liabilities Measured on a Recurring Basis Using Significant Unobservable Inputs (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Other Liabilities [Member]
Transfers to other balance sheet line items				$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value				0		$ 23
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements				(23)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Liabilities Transfers Into Level 3				0
Fair Value Measurement With Unobservable Inputs Reconciliation, Recurring Basis, Liabilities Transfers Out Of Level 3				0
Change in unrealized gains / (losses) included in earnings for the period related to financial assets still held at the end of period				0
Derivative contracts, net [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		$ 0		6		15
Included in earnings		185	[1]	198	[2]
OCI		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		2
Sales		0		0
Settlements		0		(2)
Transfers to other balance sheet line items		(191)		(211)
Transfers into Level 3		0		0
Transferred Out of Level 3 in The Fair Value Hierarchy		0		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Other Income		12	[1],[3]	7	[2],[4]
Trading Securities [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value				6		104
Included in earnings				197
OCI				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases				2
Sales				(88)
Settlements				(2)
Transfers to other balance sheet line items				(211)
Transfers into Level 3				0
Transferred Out of Level 3 in The Fair Value Hierarchy				0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Other Income	[4]			7
US States and Political Subdivisions Debt Securities [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		0		4		5
Included in earnings		0		0
OCI		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		0
Sales		0		0
Settlements		(4)		(1)
Transfers to other balance sheet line items		0		0
Transfers into Level 3		0		0
Transferred Out of Level 3 in The Fair Value Hierarchy		0		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Other Income		0		0
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		59		74		94
Included in earnings		(1)		0
OCI		(1)	[5]	(1)	[6]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		0
Sales		0		0
Settlements		(15)		(21)
Transfers to other balance sheet line items		0		0
Transfers into Level 3		0		0
Transferred Out of Level 3 in The Fair Value Hierarchy		0		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Other Income		(1)		0
Asset-backed Securities [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		8		10		12
Included in earnings		0		0
OCI		(1)	[5]	(1)	[6]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		0
Sales		0		0
Settlements		(3)		(3)
Transfers to other balance sheet line items		0		0
Transfers into Level 3		0		0
Transferred Out of Level 3 in The Fair Value Hierarchy		0		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Other Income		0		0
Other Debt Obligations [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value				0		89
Included in earnings	[7]			(1)
OCI				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases				0
Sales				(88)
Settlements				0
Transfers to other balance sheet line items				0
Transfers into Level 3				0
Transferred Out of Level 3 in The Fair Value Hierarchy				0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Other Income				0
Corporate Debt Securities [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		5		5		5
Included in earnings		0		0
OCI		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		0
Sales		0		0
Settlements		0		0
Transfers to other balance sheet line items		0		0
Transfers into Level 3		0		0
Transferred Out of Level 3 in The Fair Value Hierarchy		0		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Other Income		0		0
Equity Securities [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		418		540		440
Included in earnings		1		0
OCI		(1)	[5]	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		75		308
Sales		(1)		0
Settlements		(191)		(208)
Transfers to other balance sheet line items		0		0
Transfers into Level 3		0		0
Transferred Out of Level 3 in The Fair Value Hierarchy		(5)		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Other Income		0		0
Available-for-sale Securities [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		490		633		556
Included in earnings		0		0
OCI		(1)	[5]	(2)	[6]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		75		308
Sales		(1)		0
Settlements		(213)		(233)
Transfers to other balance sheet line items		0		0
Transfers into Level 3		0		0
Transferred Out of Level 3 in The Fair Value Hierarchy		(5)		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Other Income		(1)		0
Residential Mortgage, Loans Held For Sale [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		0		12		5
Included in earnings		0		(1)	[8]
OCI		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		0
Sales		(25)		(35)
Settlements		(1)		0
Transfers to other balance sheet line items		(4)		(5)
Transfers into Level 3		26		52
Transferred Out of Level 3 in The Fair Value Hierarchy		(8)		(4)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Other Income		0		(1)	[4],[8]
Loans Held For Investment [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		196		222		$ 257
Included in earnings		0	[9]	(2)	[8]
OCI		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		0
Sales		0		0
Settlements		(34)		(44)
Transfers to other balance sheet line items		(3)		(1)
Transfers into Level 3		5		10
Transferred Out of Level 3 in The Fair Value Hierarchy		0		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Other Income		$ (1)	[3],[9]	$ (2)	[4],[8]

[1] Includes issuances, fair value changes, and expirations. Amount related to residential IRLCs is recognized in Mortgage production related income, amount related to commercial IRLCs is recognized in Commercial real estate related income, and amount related to Visa derivative liability is recognized in Other noninterest expense.

[2] Amounts recognized in OCI are included in change in net unrealized gains/(losses) on securities AFS, net of tax.

[3] Change in unrealized gains/(losses) included in earnings during the period related to financial assets still held at December 31, 2017.

[4] Change in unrealized gains/(losses) included in earnings during the period related to financial assets/liabilities still held at December 31, 2016.

[5] Amounts recognized in OCI are included in change in net unrealized gains on securities AFS, net of tax.

[6] Amounts recognized in OCI are included in change in net unrealized gains/(losses) on securities AFS, net of tax.

[7] Includes issuances, fair value changes, and expirations. Amount related to residential IRLCs is recognized in Mortgage production related income and amount related to Visa derivative liability is recognized in Other noninterest expense.

[8] Amounts are generally included in Mortgage production related income; however, the mark on certain fair value loans is included in Other noninterest income.

[9] Amounts are generally included in Mortgage production related income; however, the mark on certain fair value loans is included in Other noninterest income.