Business Segment Reporting (Detail) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2018 USD ($)		Sep. 30, 2017 USD ($)	[1],[2]	Sep. 30, 2018 USD ($) segments		Sep. 30, 2017 USD ($)	[3],[4]
Number of Operating Segments | segments					2
Average Total Loans Held for Investment	$ 145,995		$ 144,706		$ 144,368		$ 144,276
Average Total Deposits	159,348		159,419		159,159		159,145
Average Total Assets	207,395		205,738		205,370		204,833
Average Total Liabilities	183,120		181,165		181,046		180,702
Average Total Equity	24,275		24,573		24,324		24,131
Interest Income (Expense), Net	1,512		1,430		4,440		4,199
Fully Taxable Equivalent Adjustment	22		37		65		107
Net Interest Income Including Fully Taxable Equivalent Adjustment	1,534	[5]	1,467	[6]	4,505	[7]	4,306	[8]
Provision for Loan, Lease, and Other Losses	61	[9]	120	[10]	121	[11]	330	[12]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	1,473		1,347		4,384		3,976
Noninterest Income	782	[13]	846	[14]	2,408	[15]	2,520	[16]
Noninterest Expense	1,384		1,391		4,191		4,243
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	871		802		2,601		2,253
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	117	[17]	262	[18]	477	[19]	713	[20]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	754		540		2,124		1,540
Net Income (Loss) Attributable to Noncontrolling Interest	2		2		7		7
Net Income (Loss) Attributable to Parent	752		538		2,117		1,533
Consumer [Member]
Average Total Loans Held for Investment	75,414		74,742		75,122		73,613
Average Total Deposits	111,930		109,774		111,025		109,301
Average Total Assets	86,112		84,345		85,124		83,310
Average Total Liabilities	112,879		110,713		111,928		110,264
Average Total Equity	0		0		0		0
Interest Income (Expense), Net	1,079		999		3,144		2,915
Fully Taxable Equivalent Adjustment	0		0		0		0
Net Interest Income Including Fully Taxable Equivalent Adjustment	1,079	[5]	999	[6]	3,144	[7]	2,915	[8]
Provision for Loan, Lease, and Other Losses	36	[9]	140	[10]	101	[11]	310	[12]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	1,043		859		3,043		2,605
Noninterest Income	445		482		1,349		1,427
Noninterest Expense	994		927		2,995		2,939
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	494		414		1,397		1,093
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	113	[17]	150	[18]	316	[19]	395	[20]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	381		264		1,081		698
Net Income (Loss) Attributable to Noncontrolling Interest	0		0		0		0
Net Income (Loss) Attributable to Parent	381		264		1,081		698
Wholesale [Member]
Average Total Loans Held for Investment	70,485		68,568		69,155		69,303
Average Total Deposits	47,773		49,515		48,259		49,724
Average Total Assets	84,766		82,573		83,001		82,916
Average Total Liabilities	54,284		55,054		54,383		55,322
Average Total Equity	0		0		0		0
Interest Income (Expense), Net	550		511		1,605		1,490
Fully Taxable Equivalent Adjustment	22		36		63		105
Net Interest Income Including Fully Taxable Equivalent Adjustment	572	[5]	547	[6]	1,668	[7]	1,595	[8]
Provision for Loan, Lease, and Other Losses	25	[9]	(19)	[10]	19	[11]	19	[12]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	547		566		1,649		1,576
Noninterest Income	373		397		1,124		1,169
Noninterest Expense	433		421		1,307		1,284
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	487		542		1,466		1,461
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	115	[17]	201	[18]	346	[19]	544	[20]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	372		341		1,120		917
Net Income (Loss) Attributable to Noncontrolling Interest	0		0		0		0
Net Income (Loss) Attributable to Parent	372		341		1,120		917
Corporate Other [Member]
Average Total Loans Held for Investment	96		1,399		93		1,362
Average Total Deposits	212		189		205		149
Average Total Assets	35,612		36,286		35,563		35,903
Average Total Liabilities	16,481		15,406		15,038		15,110
Average Total Equity	0		0		0		0
Interest Income (Expense), Net	(49)		(5)		(120)		29
Fully Taxable Equivalent Adjustment	1		1		2		2
Net Interest Income Including Fully Taxable Equivalent Adjustment	(48)	[5]	(4)	[6]	(118)	[7]	31	[8]
Provision for Loan, Lease, and Other Losses	0	[9]	0	[10]	0	[11]	0	[12]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	(48)		(4)		(118)		31
Noninterest Income	10		19		50		59
Noninterest Expense	(38)		48		(95)		34
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	0		(33)		27		56
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	(52)	[17]	(18)	[18]	(29)	[19]	(11)	[20]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	52		(15)		56		67
Net Income (Loss) Attributable to Noncontrolling Interest	2		2		7		7
Net Income (Loss) Attributable to Parent	50		(17)		49		60
Reconciling Items
Average Total Loans Held for Investment	0		(3)		(2)		(2)
Average Total Deposits	(567)		(59)		(330)		(29)
Average Total Assets	905		2,534		1,682		2,704
Average Total Liabilities	(524)		(8)		(303)		6
Average Total Equity	24,275		24,573		24,324		24,131
Interest Income (Expense), Net	(68)		(75)		(189)		(235)
Fully Taxable Equivalent Adjustment	(1)		0		0		0
Net Interest Income Including Fully Taxable Equivalent Adjustment	(69)	[5]	(75)	[6]	(189)	[7]	(235)	[8]
Provision for Loan, Lease, and Other Losses	0	[9]	(1)	[10]	1	[11]	1	[12]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	(69)		(74)		(190)		(236)
Noninterest Income	(46)		(52)		(115)		(135)
Noninterest Expense	(5)		(5)		(16)		(14)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(110)		(121)		(289)		(357)
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	(59)	[17]	(71)	[18]	(156)	[19]	(215)	[20]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(51)		(50)		(133)		(142)
Net Income (Loss) Attributable to Noncontrolling Interest	0		0		0		0
Net Income (Loss) Attributable to Parent	$ (51)		$ (50)		$ (133)		$ (142)

[1] During the fourth quarter of 2017, the Company sold PAC, the results of which were previously reported within the Wholesale business segment. For all periods prior to January 1, 2018, PAC's financial results, including the gain on sale, have been transferred to Corporate Other for enhanced comparability of the Wholesale business segment excluding PAC.

[2] During the second quarter of 2018, certain of the Company's business banking clients were transferred from the Wholesale business segment to the Consumer business segment. For all periods prior to the second quarter of 2018, the corresponding financial results have been transferred to the Consumer business segment for comparability purposes.

[3] During the fourth quarter of 2017, the Company sold PAC, the results of which were previously reported within the Wholesale business segment. For all periods prior to January 1, 2018, PAC's financial results, including the gain on sale, have been transferred to Corporate Other for enhanced comparability of the Wholesale business segment excluding PAC.

[4] During the second quarter of 2018, certain of the Company's business banking clients were transferred from the Wholesale business segment to the Consumer business segment. For all periods prior to the second quarter of 2018, the corresponding financial results have been transferred to the Consumer business segment for comparability purposes.

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

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

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

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

[9] 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.

[10] 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.

[11] 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.

[12] 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 balan

[13] Amounts are presented in accordance with ASC Topic 606, Revenue from Contracts with Customers, except for out of scope amounts.

[14] Amounts for periods prior to January 1, 2018 are presented in accordance with ASC Topic 605, Revenue Recognition, and have not been restated to conform with ASC Topic 606, Revenue from Contracts with Customers.

[15] Amounts are presented in accordance with ASC Topic 606, Revenue from Contracts with Customers, except for out of scope amounts.

[16] Amounts for periods prior to January 1, 2018 are presented in accordance with ASC Topic 605, Revenue Recognition, and have not been restated to conform with ASC Topic 606, Revenue from Contracts with Customers.

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

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

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

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