Business Segment Reporting (Detail) $ in Millions	3 Months Ended						6 Months Ended
	Jun. 30, 2019 USD ($)		Mar. 31, 2019 USD ($)	Jun. 30, 2018 USD ($)		Mar. 31, 2018 USD ($)	Jun. 30, 2019 USD ($) segments		Jun. 30, 2018 USD ($)
Number of Operating Segments | segments							2
Average Total Loans Held for Investment	$ 156,224			$ 144,156			$ 155,246		$ 143,542
Average Total Deposits	159,854			158,957			159,887		159,063
Average Total Assets	220,827			204,548			219,124		204,341
Average Total Liabilities	195,618			180,453			194,284		179,992
Average Total Equity	25,209			24,095			24,840		24,349
Interest Income (Expense), Net	1,535			1,488			3,078		2,928
Fully Taxable Equivalent Adjustment	22			22			45		43
Net Interest Income Including Fully Taxable Equivalent Adjustment	1,557	[1]		1,510	[2]		3,123	[3]	2,971	[4]
Provision for Loan, Lease, and Other Losses	127	[5]		32	[6]		280	[7]	60	[8]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	1,430			1,478			2,843		2,911
Noninterest Income	1,025			829			1,810		1,626
Noninterest Expense	1,638			1,390			3,128		2,807
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	817			917			1,525		1,730
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	127	[9]		193	[10]		253	[11]	361	[12]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	690			724			1,272		1,369
Net Income (Loss) Attributable to Noncontrolling Interest	2			2			4		4
Net Income (Loss) Attributable to Parent	688		$ 580	722		$ 643	1,268		1,365
Consumer [Member]
Average Total Loans Held for Investment	79,280			74,626			78,982		74,733
Average Total Deposits	112,824			111,532			112,533		110,509
Average Total Assets	88,668			84,486			88,351		84,380
Average Total Liabilities	113,770			112,417			113,473		111,387
Average Total Equity	0			0			0		0
Interest Income (Expense), Net	1,078			1,032			2,154		2,030
Fully Taxable Equivalent Adjustment	0			0			0		0
Net Interest Income Including Fully Taxable Equivalent Adjustment	1,078	[1]		1,032	[2]		2,154	[3]	2,030	[4]
Provision for Loan, Lease, and Other Losses	44	[5]		7	[6]		127	[7]	65	[8]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	1,034			1,025			2,027		1,965
Noninterest Income	489			452			936		903
Noninterest Expense	991			991			2,004		1,994
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	532			486			959		874
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	122	[9]		110	[10]		219	[11]	196	[12]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	410			376			740		678
Net Income (Loss) Attributable to Noncontrolling Interest	0			0			0		0
Net Income (Loss) Attributable to Parent	410			376			740		678
Wholesale [Member]
Average Total Loans Held for Investment	76,854			69,443			76,176		68,725
Average Total Deposits	44,093			44,456			44,243		45,545
Average Total Assets	92,418			82,928			91,277		82,329
Average Total Liabilities	50,893			50,504			50,911		51,476
Average Total Equity	0			0			0		0
Interest Income (Expense), Net	537			531			1,078		1,040
Fully Taxable Equivalent Adjustment	22			22			44		42
Net Interest Income Including Fully Taxable Equivalent Adjustment	559	[1]		553	[2]		1,122	[3]	1,082	[4]
Provision for Loan, Lease, and Other Losses	82	[5]		25	[6]		152	[7]	(5)	[8]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	477			528			970		1,087
Noninterest Income	404			388			769		728
Noninterest Expense	455			425			919		873
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	426			491			820		942
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	102	[9]		117	[10]		195	[11]	224	[12]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	324			374			625		718
Net Income (Loss) Attributable to Noncontrolling Interest	0			0			0		0
Net Income (Loss) Attributable to Parent	324			374			625		718
Corporate Other [Member]
Average Total Loans Held for Investment	89			90			89		87
Average Total Deposits	3,179			3,204			3,450		3,219
Average Total Assets	38,178			35,427			38,001		35,553
Average Total Liabilities	31,064			17,736			30,129		17,320
Average Total Equity	0			0			0		0
Interest Income (Expense), Net	(76)			(41)			(149)		(65)
Fully Taxable Equivalent Adjustment	0			1			1		1
Net Interest Income Including Fully Taxable Equivalent Adjustment	(76)	[1]		(40)	[2]		(148)	[3]	(64)	[4]
Provision for Loan, Lease, and Other Losses	0	[5]		0	[6]		0	[7]	0	[8]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	(76)			(40)			(148)		(64)
Noninterest Income	177			26			196		64
Noninterest Expense	198			(23)			216		(49)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(97)			9			(168)		49
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	(50)	[9]		13	[10]		(74)	[11]	28	[12]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(47)			(4)			(94)		21
Net Income (Loss) Attributable to Noncontrolling Interest	2			2			5		5
Net Income (Loss) Attributable to Parent	(49)			(6)			(99)		16
Reconciling Items
Average Total Loans Held for Investment	1			(3)			(1)		(3)
Average Total Deposits	(242)			(235)			(339)		(210)
Average Total Assets	1,563			1,707			1,495		2,079
Average Total Liabilities	(109)			(204)			(229)		(191)
Average Total Equity	25,209			24,095			24,840		24,349
Interest Income (Expense), Net	(4)			(34)			(5)		(77)
Fully Taxable Equivalent Adjustment	0			(1)			0		0
Net Interest Income Including Fully Taxable Equivalent Adjustment	(4)	[1]		(35)	[2]		(5)	[3]	(77)	[4]
Provision for Loan, Lease, and Other Losses	1	[5]		0	[6]		1	[7]	0	[8]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	(5)			(35)			(6)		(77)
Noninterest Income	(45)			(37)			(91)		(69)
Noninterest Expense	(6)			(3)			(11)		(11)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(44)			(69)			(86)		(135)
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	(47)	[9]		(47)	[10]		(87)	[11]	(87)	[12]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	3			(22)			1		(48)
Net Income (Loss) Attributable to Noncontrolling Interest	0			0			(1)		(1)
Net Income (Loss) Attributable to Parent	$ 3			$ (22)			$ 2		$ (47)

[1] Presented on a matched maturity funds transfer price basis for the segments.

[2] Presented on a matched maturity funds transfer price basis for the segments.

[3] Presented on a matched maturity funds transfer price basis for the segments.

[4] Presented on a matched maturity funds transfer price basis for the segments.

[5] Provision for credit losses represents net charge-offs by segment combined with an allocation to the segments for the provision attributable to quarterly changes in the ALLL and unfunded commitment reserve balances.

[6] Provision for credit losses represents net charge-offs by segment combined with an allocation to the segments for the provision attributable to quarterly changes in the ALLL and unfunded commitment reserve balances.

[7] Provision for credit losses represents net charge-offs by segment combined with an allocation to the segments for the provision attributable to quarterly changes in the ALLL and unfunded commitment reserve balances.

[8] Provision/(benefit) for credit losses represents net charge-offs by segment combined with an allocation to the segments for the provision/(benefit) attributable to quarterly changes in the ALLL and unfunded commitment reserve balances.

[9] Includes regular provision for income taxes as well as FTE income and tax credit adjustment reversals.

[10] Includes regular provision for income taxes as well as FTE income and tax credit adjustment reversals.

[11] Includes regular provision for income taxes as well as FTE income and tax credit adjustment reversals.

[12] Includes regular provision for income taxes as well as FTE income and tax credit adjustment reversals.