Business Segment Reporting (Detail) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2019 USD ($)		Sep. 30, 2018 USD ($)		Sep. 30, 2019 USD ($) segments		Sep. 30, 2018 USD ($)
Number of Operating Segments | segments					2
Average Total Loans Held for Investment	$ 157,612		$ 145,995		$ 156,044		$ 144,368
Average Total Deposits	162,533		159,348		160,779		159,159
Average Total Assets	224,747		207,395		221,019		205,370
Average Total Liabilities	198,521		183,120		195,712		181,046
Average Total Equity	26,226		24,275		25,307		24,324
Interest Income (Expense), Net	1,510		1,512		4,589		4,440
Fully Taxable Equivalent Adjustment	22		22		66		65
Net Interest Income Including Fully Taxable Equivalent Adjustment	1,532	[1]	1,534	[2]	4,655	[3]	4,505	[4]
Provision for Loan, Lease, and Other Losses	132	[5]	61	[6]	412	[7]	121	[8]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	1,400		1,473		4,243		4,384
Noninterest Income	843		782		2,653		2,408
Noninterest Expense	1,474		1,384		4,602		4,191
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	769		871		2,294		2,601
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	144	[9]	117	[10]	396	[11]	477	[12]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	625		754		1,898		2,124
Net Income (Loss) Attributable to Noncontrolling Interest	2		2		7		7
Net Income (Loss) Attributable to Parent	623		752		1,891		2,117
Consumer [Member]
Average Total Loans Held for Investment	80,414		75,234		79,473		74,907
Average Total Deposits	114,132		111,950		113,067		111,008
Average Total Assets	90,329		85,933		89,026		84,909
Average Total Liabilities	114,989		112,898		113,979		111,909
Average Total Equity	0		0		0		0
Interest Income (Expense), Net	1,068		1,056		3,222		3,087
Fully Taxable Equivalent Adjustment	0		0		0		0
Net Interest Income Including Fully Taxable Equivalent Adjustment	1,068	[1]	1,056	[2]	3,222	[3]	3,087	[4]
Provision for Loan, Lease, and Other Losses	77	[5]	36	[6]	204	[7]	102	[8]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	991		1,020		3,018		2,985
Noninterest Income	479		444		1,415		1,347
Noninterest Expense	1,025		991		3,029		2,984
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	445		473		1,404		1,348
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	102	[9]	108	[10]	321	[11]	305	[12]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	343		365		1,083		1,043
Net Income (Loss) Attributable to Noncontrolling Interest	0		0		0		0
Net Income (Loss) Attributable to Parent	343		365		1,083		1,043
Wholesale [Member]
Average Total Loans Held for Investment	77,107		70,669		76,481		69,375
Average Total Deposits	45,817		44,702		44,777		45,247
Average Total Assets	93,584		84,909		92,046		83,193
Average Total Liabilities	52,471		51,215		51,441		51,375
Average Total Equity	0		0		0		0
Interest Income (Expense), Net	529		539		1,607		1,580
Fully Taxable Equivalent Adjustment	21		22		65		63
Net Interest Income Including Fully Taxable Equivalent Adjustment	550	[1]	561	[2]	1,672	[3]	1,643	[4]
Provision for Loan, Lease, and Other Losses	56	[5]	24	[6]	208	[7]	19	[8]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	494		537		1,464		1,624
Noninterest Income	368		368		1,137		1,096
Noninterest Expense	457		432		1,382		1,307
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	405		473		1,219		1,413
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	96	[9]	112	[10]	289	[11]	334	[12]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	309		361		930		1,079
Net Income (Loss) Attributable to Noncontrolling Interest	0		0		0		0
Net Income (Loss) Attributable to Parent	309		361		930		1,079
Corporate Other [Member]
Average Total Loans Held for Investment	91		93		90		89
Average Total Deposits	2,779		3,264		3,224		3,234
Average Total Assets	38,557		35,647		38,189		35,585
Average Total Liabilities	31,126		19,531		30,465		18,065
Average Total Equity	0		0		0		0
Interest Income (Expense), Net	(79)		(46)		(222)		(111)
Fully Taxable Equivalent Adjustment	0		1		1		2
Net Interest Income Including Fully Taxable Equivalent Adjustment	(79)	[1]	(45)	[2]	(221)	[3]	(109)	[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	(79)		(45)		(221)		(109)
Noninterest Income	34		16		230		81
Noninterest Expense	(5)		(35)		207		(83)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(40)		6		(198)		55
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	(10)	[9]	(51)	[10]	(81)	[11]	(23)	[12]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(30)		57		(117)		78
Net Income (Loss) Attributable to Noncontrolling Interest	2		2		7		7
Net Income (Loss) Attributable to Parent	(32)		55		(124)		71
Reconciling Items
Average Total Loans Held for Investment	0		(1)		0		(3)
Average Total Deposits	(195)		(568)		(289)		(330)
Average Total Assets	2,277		906		1,758		1,683
Average Total Liabilities	(65)		(524)		(173)		(303)
Average Total Equity	26,226		24,275		25,307		24,324
Interest Income (Expense), Net	(8)		(37)		(18)		(116)
Fully Taxable Equivalent Adjustment	1		(1)		0		0
Net Interest Income Including Fully Taxable Equivalent Adjustment	(7)	[1]	(38)	[2]	(18)	[3]	(116)	[4]
Provision for Loan, Lease, and Other Losses	(1)	[5]	1	[6]	0	[7]	0	[8]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	(6)		(39)		(18)		(116)
Noninterest Income	(38)		(46)		(129)		(116)
Noninterest Expense	(3)		(4)		(16)		(17)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(41)		(81)		(131)		(215)
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	(44)	[9]	(52)	[10]	(133)	[11]	(139)	[12]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	3		(29)		2		(76)
Net Income (Loss) Attributable to Noncontrolling Interest	0		0		0		0
Net Income (Loss) Attributable to Parent	$ 3		$ (29)		$ 2		$ (76)

[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 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.

[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.