Business Segment Reporting (Detail) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2018 USD ($)		Jun. 30, 2017 USD ($)	[1],[2]	Jun. 30, 2018 USD ($) segments		Jun. 30, 2017 USD ($)	[3],[4]
Number of Operating Segments | segments					2
Average Total Loans Held for Investment	$ 144,156		$ 144,440		$ 143,542		$ 144,058
Average Total Deposits	158,957		159,136		159,063		159,006
Average Total Assets	204,548		204,494		204,341		204,374
Average Total Liabilities	180,453		180,355		179,992		180,468
Average Total Equity	24,095		24,139		24,349		23,906
Interest Income (Expense), Net	1,488		1,403		2,928		2,769
Fully Taxable Equivalent Adjustment	22		36		43		70
Net Interest Income Including Fully Taxable Equivalent Adjustment	1,510	[5]	1,439	[6]	2,971	[7]	2,839	[8]
Provision for Loan, Lease, and Other Losses	32	[9]	90	[10]	60	[11]	209	[12]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	1,478		1,349		2,911		2,630
Noninterest Income	829	[13]	827	[14]	1,626	[15]	1,674	[16]
Noninterest Expense	1,390		1,388		2,807		2,853
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	917		788		1,730		1,451
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	193	[17]	258	[18]	361	[19]	451	[20]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	724		530		1,369		1,000
Net Income (Loss) Attributable to Noncontrolling Interest	2		2		4		5
Net Income (Loss) Attributable to Parent	722		528		1,365		995
Consumer [Member]
Average Total Loans Held for Investment	75,450		73,680		75,564		73,247
Average Total Deposits	111,555		109,580		110,432		108,818
Average Total Assets	85,309		83,230		85,210		82,991
Average Total Liabilities	112,438		110,555		111,309		109,792
Average Total Equity	0		0		0		0
Interest Income (Expense), Net	1,058		975		2,073		1,917
Fully Taxable Equivalent Adjustment	0		0		0		0
Net Interest Income Including Fully Taxable Equivalent Adjustment	1,058	[5]	975	[6]	2,073	[7]	1,917	[8]
Provision for Loan, Lease, and Other Losses	7	[9]	84	[10]	65	[11]	171	[12]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	1,051		891		2,008		1,746
Noninterest Income	453		473		904		945
Noninterest Expense	995		983		2,004		2,010
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	509		381		908		681
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	115	[17]	137	[18]	202	[19]	245	[20]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	394		244		706		436
Net Income (Loss) Attributable to Noncontrolling Interest	0		0		0		0
Net Income (Loss) Attributable to Parent	394		244		706		436
Wholesale [Member]
Average Total Loans Held for Investment	68,615		69,365		67,889		69,469
Average Total Deposits	47,431		49,381		48,638		50,070
Average Total Assets	82,133		82,801		81,514		82,883
Average Total Liabilities	53,481		55,006		54,568		55,700
Average Total Equity	0		0		0		0
Interest Income (Expense), Net	534		493		1,046		971
Fully Taxable Equivalent Adjustment	22		35		42		69
Net Interest Income Including Fully Taxable Equivalent Adjustment	556	[5]	528	[6]	1,088	[7]	1,040	[8]
Provision for Loan, Lease, and Other Losses	24	[9]	6	[10]	(6)	[11]	38	[12]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	532		522		1,094		1,002
Noninterest Income	388		378		751		771
Noninterest Expense	424		421		876		867
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	496		479		969		906
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	118	[17]	178	[18]	229	[19]	337	[20]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	378		301		740		569
Net Income (Loss) Attributable to Noncontrolling Interest	0		0		0		0
Net Income (Loss) Attributable to Parent	378		301		740		569
Corporate Other [Member]
Average Total Loans Held for Investment	94		1,400		92		1,344
Average Total Deposits	206		151		202		131
Average Total Assets	35,400		35,991		35,538		35,709
Average Total Liabilities	14,738		14,744		14,306		14,962
Average Total Equity	0		0		0		0
Interest Income (Expense), Net	(42)		9		(70)		34
Fully Taxable Equivalent Adjustment	1		1		1		1
Net Interest Income Including Fully Taxable Equivalent Adjustment	(41)	[5]	10	[6]	(69)	[7]	35	[8]
Provision for Loan, Lease, and Other Losses	0	[9]	1	[10]	0	[11]	0	[12]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	(41)		9		(69)		35
Noninterest Income	26		17		40		41
Noninterest Expense	(25)		(11)		(62)		(16)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	10		37		33		92
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	13	[17]	14	[18]	24	[19]	8	[20]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(3)		23		9		84
Net Income (Loss) Attributable to Noncontrolling Interest	2		2		5		5
Net Income (Loss) Attributable to Parent	(5)		21		4		79
Reconciling Items
Average Total Loans Held for Investment	(3)		(5)		(3)		(2)
Average Total Deposits	(235)		24		(209)		(13)
Average Total Assets	1,706		2,472		2,079		2,791
Average Total Liabilities	(204)		50		(191)		14
Average Total Equity	24,095		24,139		24,349		23,906
Interest Income (Expense), Net	(62)		(74)		(121)		(153)
Fully Taxable Equivalent Adjustment	(1)		0		0		0
Net Interest Income Including Fully Taxable Equivalent Adjustment	(63)	[5]	(74)	[6]	(121)	[7]	(153)	[8]
Provision for Loan, Lease, and Other Losses	1	[9]	(1)	[10]	1	[11]	0	[12]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	(64)		(73)		(122)		(153)
Noninterest Income	(38)		(41)		(69)		(83)
Noninterest Expense	(4)		(5)		(11)		(8)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(98)		(109)		(180)		(228)
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	(53)	[17]	(71)	[18]	(94)	[19]	(139)	[20]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(45)		(38)		(86)		(89)
Net Income (Loss) Attributable to Noncontrolling Interest	0		0		(1)		0
Net Income (Loss) Attributable to Parent	$ (45)		$ (38)		$ (85)		$ (89)

[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 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.

[11] 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.

[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.