LHFI by Credit Quality Indicator (Detail) - USD ($) $ in Millions		Sep. 30, 2019		Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[1]	$ 158,455		$ 151,839
Financing Receivable, Nonaccrual	[2]	600	[3]	526	[4]
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[5]	73,374		71,137
Financing Receivable, Nonaccrual		350	[3]	157	[4]
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		9,491		7,265
Financing Receivable, Nonaccrual		1	[3]	2	[4]
Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,142		2,538
Financing Receivable, Nonaccrual		0	[3]	0	[4]
Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6],[8]	28,810	[7]	28,836	[9]
Financing Receivable, Nonaccrual		125	[3],[7]	204	[4],[9]
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[8]	8,696		9,468
Financing Receivable, Nonaccrual		100	[3]	138	[4]
Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[8]	144		184
Financing Receivable, Nonaccrual		8	[3]	11	[4]
Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		12,431		10,615
Financing Receivable, Nonaccrual		11	[3]	7	[4]
Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		14,060		12,419
Financing Receivable, Nonaccrual		5	[3]	7	[4]
Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,704		1,689
Financing Receivable, Nonaccrual		0	[3]	0	[4]
Pass | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		70,739		69,095
Pass | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		9,410		7,165
Pass | Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,082		2,459
Criticized Accruing | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,285		1,885
Criticized Accruing | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		80		98
Criticized Accruing | Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		60		79
FICO Score 700 and Above [Member] | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[8]	25,985		25,764
FICO Score 700 and Above [Member] | Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[8]	7,406		8,060
FICO Score 700 and Above [Member] | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[8]	116		151
FICO Score 700 and Above [Member] | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		10,671		9,296
FICO Score 700 and Above [Member] | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		10,904		9,315
FICO Score 700 and Above [Member] | Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,145		1,142
FICO Score Between 620 and 699 | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[8]	2,219		2,367
FICO Score Between 620 and 699 | Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[8]	929		1,015
FICO Score Between 620 and 699 | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[8]	22		27
FICO Score Between 620 and 699 | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,543		1,175
FICO Score Between 620 and 699 | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,367		2,395
FICO Score Between 620 and 699 | Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		423		420
FICO Score Below 620 | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[8],[10]	606		705
FICO Score Below 620 | Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[8],[10]	361		393
FICO Score Below 620 | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[8],[10]	6		6
FICO Score Below 620 | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[10]	217		144
FICO Score Below 620 | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[10]	789		709
FICO Score Below 620 | Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[10]	$ 136		$ 127

[1] Includes LHFI of consolidated VIEs of $136 million and $153 million at September 30, 2019 and December 31, 2018, respectively.

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

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

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

[5] Includes $4.0 billion and $4.1 billion of sales-type, direct financing, and leveraged leases at September 30, 2019 and December 31, 2018, respectively. Includes $817 million and $796 million of installment loans at September 30, 2019 and December 31, 2018, respectively.

[6] Includes $124 million and $163 million measured at fair value at September 30, 2019 and December 31, 2018, respectively.

[7] Includes $124 million of LHFI measured at fair value, the majority of which were accruing current.

[8] Excludes $7.1 billion and $7.2 billion of guaranteed student loans and $457 million and $459 million of guaranteed residential mortgages at September 30, 2019 and December 31, 2018, respectively, for which there was nominal risk of principal loss due to the government guarantee.

[9] Includes $163 million of LHFI 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.