Business Segment Reporting (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) segments		Dec. 31, 2016 USD ($)	[1]	Dec. 31, 2015 USD ($)	[2]
Number of Operating Segments | segments	2
Average Total Loans Held for Investment	$ 144,216		$ 141,118		$ 133,558
Average Total Deposits	159,549		154,189		144,203
Average Total Assets	204,931		199,004		188,892
Average Total Liabilities	180,630		174,936		165,546
Average Total Equity	24,301		24,068		23,346
Interest Income (Expense), Net	5,633		5,221		4,764
Fully Taxable Equivalent Adjustment	145		138		142
Net Interest Income Including Fully Taxable Equivalent Adjustment	5,778	[3]	5,359	[4]	4,906	[5]
Provision for Loan, Lease, and Other Losses	409	[6]	444	[7]	165	[8]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	5,369		4,915		4,741
Noninterest Income	3,354		3,383		3,268
Noninterest Expense	5,764		5,468		5,160
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	2,959		2,830		2,849
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	677	[9]	943	[10]	906	[11]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	2,282		1,887		1,943
Net Income (Loss) Attributable to Noncontrolling Interest	9		9		10
Net Income (Loss) Attributable to Parent	2,273		1,878		1,933
Consumer [Member]
Average Total Loans Held for Investment	72,622		69,455		65,637
Average Total Deposits	102,820		99,424		93,789
Average Total Assets	82,507		79,118		75,204
Average Total Liabilities	103,757		100,423		94,801
Average Total Equity	0		0		0
Interest Income (Expense), Net	3,698		3,465		3,324
Fully Taxable Equivalent Adjustment	0		0		1
Net Interest Income Including Fully Taxable Equivalent Adjustment	3,698	[3]	3,465	[4]	3,325	[5]
Provision for Loan, Lease, and Other Losses	368	[6]	172	[7]	27	[8]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	3,330		3,293		3,298
Noninterest Income	1,874		2,036		1,967
Noninterest Expense	3,842		3,796		3,631
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	1,362		1,533		1,634
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	491	[9]	568	[10]	553	[11]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	871		965		1,081
Net Income (Loss) Attributable to Noncontrolling Interest	0		0		0
Net Income (Loss) Attributable to Parent	871		965		1,081
Wholesale [Member]
Average Total Loans Held for Investment	71,521		71,600		67,872
Average Total Deposits	56,618		54,713		50,373
Average Total Assets	85,227		85,494		80,903
Average Total Liabilities	62,291		60,438		56,044
Average Total Equity	0		0		0
Interest Income (Expense), Net	2,247		2,018		1,918
Fully Taxable Equivalent Adjustment	142		136		138
Net Interest Income Including Fully Taxable Equivalent Adjustment	2,389	[3]	2,154	[4]	2,056	[5]
Provision for Loan, Lease, and Other Losses	41	[6]	272	[7]	137	[8]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	2,348		1,882		1,919
Noninterest Income	1,710		1,356		1,285
Noninterest Expense	1,869		1,676		1,523
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	2,189		1,562		1,681
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	816	[9]	583	[10]	628	[11]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	1,373		979		1,053
Net Income (Loss) Attributable to Noncontrolling Interest	0		0		0
Net Income (Loss) Attributable to Parent	1,373		979		1,053
Corporate Other [Member]
Average Total Loans Held for Investment	76		66		60
Average Total Deposits	175		124		101
Average Total Assets	34,567		31,952		29,668
Average Total Liabilities	14,610		14,148		14,771
Average Total Equity	0		0		0
Interest Income (Expense), Net	(44)		101		152
Fully Taxable Equivalent Adjustment	3		2		3
Net Interest Income Including Fully Taxable Equivalent Adjustment	(41)	[3]	103	[4]	155	[5]
Provision for Loan, Lease, and Other Losses	0	[6]	0	[7]	0	[8]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	(41)		103		155
Noninterest Income	(33)		138		137
Noninterest Expense	73		13		17
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(147)		228		275
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	(355)	[9]	59	[10]	81	[11]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	208		169		194
Net Income (Loss) Attributable to Noncontrolling Interest	9		9		10
Net Income (Loss) Attributable to Parent	199		160		184
Reconciling Items
Average Total Loans Held for Investment	(3)		(3)		(11)
Average Total Deposits	(64)		(72)		(60)
Average Total Assets	2,630		2,440		3,117
Average Total Liabilities	(28)		(73)		(70)
Average Total Equity	24,301		24,068		23,346
Interest Income (Expense), Net	(268)		(363)		(630)
Fully Taxable Equivalent Adjustment	0		0		0
Net Interest Income Including Fully Taxable Equivalent Adjustment	(268)	[3]	(363)	[4]	(630)	[5]
Provision for Loan, Lease, and Other Losses	0	[6]	0	[7]	1	[8]
Net Interest Income After Provision For Credit Losses and Taxable Equivalent Adjustment	(268)		(363)		(631)
Noninterest Income	(197)		(147)		(121)
Noninterest Expense	(20)		(17)		(11)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(445)		(493)		(741)
Income Tax Expense (Benefit) Including Fully Taxable Equivalent Adjustment Reversal	(275)	[9]	(267)	[10]	(356)	[11]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(170)		(226)		(385)
Net Income (Loss) Attributable to Noncontrolling Interest	0		0		0
Net Income (Loss) Attributable to Parent	$ (170)		$ (226)		$ (385)

[1] Beginning in the second quarter of 2017, the Company realigned its business segment structure from three segments to two segments. Specifically, the Company retained the previous composition of the Wholesale Banking segment and changed the basis of presentation of the Consumer Banking and Private Wealth Management segment and Mortgage Banking segment such that those segments were combined into a single Consumer segment. Accordingly, business segment information presented for the year ended December 31, 2016 has been revised to conform to the new business segment structure and updated internal funds transfer pricing methodology for consistent presentation.

[2] Beginning in the second quarter of 2017, the Company realigned its business segment structure from three segments to two segments. Specifically, the Company retained the previous composition of the Wholesale Banking segment and changed the basis of presentation of the Consumer Banking and Private Wealth Management segment and Mortgage Banking segment such that those segments were combined into a single Consumer segment. Accordingly, business segment information presented for the year ended December 31, 2015 has been revised to conform to the new business segment structure and updated internal funds transfer pricing methodology for consistent presentation.

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

[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.