LHFI by Credit Quality Indicator (Detail) - USD ($) $ in Millions		Jun. 30, 2019		Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		$ 156,589		$ 151,839
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	536	[2]	526	[3]
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	72,971		71,137
Financing Receivable, Recorded Investment, Nonaccrual Status		258	[2]	157	[3]
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		8,655		7,265
Financing Receivable, Recorded Investment, Nonaccrual Status		2	[2]	2	[3]
Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,365		2,538
Financing Receivable, Recorded Investment, Nonaccrual Status		0	[2]	0	[3]
Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6],[7]	28,794	[5]	28,836	[8]
Financing Receivable, Recorded Investment, Nonaccrual Status		144	[2],[5]	204	[3],[8]
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	8,902		9,468
Financing Receivable, Recorded Investment, Nonaccrual Status		109	[2]	138	[3]
Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	156		184
Financing Receivable, Recorded Investment, Nonaccrual Status		8	[2]	11	[3]
Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		11,817		10,615
Financing Receivable, Recorded Investment, Nonaccrual Status		10	[2]	7	[3]
Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		13,598		12,419
Financing Receivable, Recorded Investment, Nonaccrual Status		5	[2]	7	[3]
Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,690		1,689
Financing Receivable, Recorded Investment, Nonaccrual Status		0	[2]	0	[3]
Pass | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		70,532		69,095
Pass | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		8,526		7,165
Pass | Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,311		2,459
Criticized Accruing | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,181		1,885
Criticized Accruing | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		127		98
Criticized Accruing | Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		54		79
FICO Score 700 and Above [Member] | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	25,895		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	[6]	7,573		8,060
FICO Score 700 and Above [Member] | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	125		151
FICO Score 700 and Above [Member] | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		10,220		9,296
FICO Score 700 and Above [Member] | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		10,506		9,315
FICO Score 700 and Above [Member] | Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,147		1,142
FICO Score Between 620 and 699 | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	2,278		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	[6]	952		1,015
FICO Score Between 620 and 699 | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6]	26		27
FICO Score Between 620 and 699 | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,428		1,175
FICO Score Between 620 and 699 | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,326		2,395
FICO Score Between 620 and 699 | Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		416		420
FICO Score Below 620 | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6],[9]	621		705
FICO Score Below 620 | Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6],[9]	377		393
FICO Score Below 620 | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[6],[9]	5		6
FICO Score Below 620 | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[9]	169		144
FICO Score Below 620 | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[9]	766		709
FICO Score Below 620 | Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[9]	$ 127		$ 127

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

[2] Includes nonaccruing LHFI past due 90 days or more of $301 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.

[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 $4.1 billion of sales-type, direct financing, and leveraged leases at both June 30, 2019 and December 31, 2018. Includes $862 million and $796 million of installment loans at June 30, 2019 and December 31, 2018, respectively.

[5] Includes $127 million of LHFI measured at fair value, the majority of which were accruing current.

[6] Excludes $7.2 billion of guaranteed student loans at both June 30, 2019 and December 31, 2018, and $439 million and $459 million of guaranteed residential mortgages at June 30, 2019 and December 31, 2018, respectively, for which there was nominal risk of principal loss due to the government guarantee.

[7] Includes $127 million and $163 million of LHFI measured at fair value at June 30, 2019 and December 31, 2018, respectively.

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

[9] 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.