LHFI by Credit Quality Indicator (Detail) - USD ($) $ in Millions		Dec. 31, 2018		Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[1]	$ 151,839		$ 143,181
Financing Receivable, Recorded Investment, Nonaccrual Status	[2]	526	[3]	674	[4]
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[5]	71,137		66,356
Financing Receivable, Recorded Investment, Nonaccrual Status		157	[3]	215	[4]
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		7,265		5,317
Financing Receivable, Recorded Investment, Nonaccrual Status		2	[3]	24	[4]
Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,538		3,804
Financing Receivable, Recorded Investment, Nonaccrual Status		0	[3]	1	[4]
Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7],[8]	28,836	[6]	27,136	[9]
Financing Receivable, Recorded Investment, Nonaccrual Status		204	[3],[6]	206	[4],[9]
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7]	9,468		10,626
Financing Receivable, Recorded Investment, Nonaccrual Status		138	[3]	203	[4]
Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7]	184		298
Financing Receivable, Recorded Investment, Nonaccrual Status		11	[3]	11	[4]
Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		10,615		8,729
Financing Receivable, Recorded Investment, Nonaccrual Status		7	[3]	7	[4]
Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		12,419		12,140
Financing Receivable, Recorded Investment, Nonaccrual Status		7	[3]	7	[4]
Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,689		1,582
Financing Receivable, Recorded Investment, Nonaccrual Status		0	[3]	0	[4]
Pass | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		69,095		64,546
Pass | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		7,165		5,126
Pass | Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,459		3,770
Criticized Accruing | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,885		1,595
Criticized Accruing | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		98		167
Criticized Accruing | Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		79		33
FICO Score 700 and Above [Member] | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7]	25,764		23,602
FICO Score 700 and Above [Member] | Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7]	8,060		8,946
FICO Score 700 and Above [Member] | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7]	151		240
FICO Score 700 and Above [Member] | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		9,642		7,929
FICO Score 700 and Above [Member] | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		9,315		9,094
FICO Score 700 and Above [Member] | Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,142		1,088
FICO Score Between 620 and 699 | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7]	2,367		2,721
FICO Score Between 620 and 699 | Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7]	1,015		1,242
FICO Score Between 620 and 699 | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7]	27		50
FICO Score Between 620 and 699 | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		935		757
FICO Score Between 620 and 699 | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,395		2,344
FICO Score Between 620 and 699 | Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		420		395
FICO Score Below 620 | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7],[10]	705		813
FICO Score Below 620 | Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7],[10]	393		438
FICO Score Below 620 | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7],[10]	6		8
FICO Score Below 620 | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[10]	38		43
FICO Score Below 620 | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[10]	709		702
FICO Score Below 620 | Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[10]	$ 127		$ 99

[1] Includes loans of consolidated VIEs of $153 million and $179 million at December?31, 2018 and December?31, 2017, respectively.

[2] Nonaccruing restructured loans are included in total nonaccrual loans/NPLs.

[3] Includes nonaccruing LHFI past due 90 days or more of $306 million. Nonaccruing LHFI past due fewer than 90 days include nonaccrual loans modified in TDRs, performing second lien loans where the first lien loan is nonperforming, and certain energy-related commercial loans.

[4] Includes nonaccruing LHFI past due 90 days or more of $357 million. Nonaccruing LHFI past due fewer than 90 days include nonaccrual loans modified in TDRs, performing second lien loans where the first lien loan is nonperforming, and certain energy-related commercial loans.

[5] Includes $4.1 billion and $3.7 billion of lease financing, and $796 million and $778 million of installment loans at December 31, 2018 and 2017, respectively.

[6] Includes $163 million of loans measured at fair value, the majority of which were accruing current.

[7] Excludes $7.2 billion and $6.6 billion of guaranteed student loans and $459 million and $560 million of guaranteed residential mortgages at December 31, 2018 and 2017, respectively, for which there was nominal risk of principal loss due to the government guarantee.

[8] Includes $163 million and $196 million of LHFI measured at fair value at December 31, 2018 and 2017, respectively.

[9] Includes $196 million of loans measured at fair value, the majority of which were accruing current.

[10] For substantially all loans with refreshed FICO scores below 620, the borrower’s FICO score at the time of origination exceeded 620 but has since deteriorated as the loan has seasoned.