LHFI by Credit Quality Indicator (Detail) - USD ($) $ in Millions		Mar. 31, 2019		Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[1]	$ 155,233		$ 151,839
Financing Receivable, Recorded Investment, Nonaccrual Status	[2]	522	[3]	526	[4]
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[5]	73,278		71,137
Financing Receivable, Recorded Investment, Nonaccrual Status		197	[3]	157	[4]
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		7,889		7,265
Financing Receivable, Recorded Investment, Nonaccrual Status		2	[3]	2	[4]
Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,562		2,538
Financing Receivable, Recorded Investment, Nonaccrual Status		0	[3]	0	[4]
Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7],[8]	28,461	[6]	28,836	[9]
Financing Receivable, Recorded Investment, Nonaccrual Status		178	[3],[6]	204	[4],[9]
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7]	9,167		9,468
Financing Receivable, Recorded Investment, Nonaccrual Status		124	[3]	138	[4]
Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7]	167		184
Financing Receivable, Recorded Investment, Nonaccrual Status		8	[3]	11	[4]
Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		11,029		10,615
Financing Receivable, Recorded Investment, Nonaccrual Status		8	[3]	7	[4]
Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		13,268		12,419
Financing Receivable, Recorded Investment, Nonaccrual Status		5	[3]	7	[4]
Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,637		1,689
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		71,078		69,095
Pass | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		7,761		7,165
Pass | Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,543		2,459
Criticized Accruing | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,003		1,885
Criticized Accruing | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		126		98
Criticized Accruing | Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		19		79
FICO Score 700 and Above [Member] | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7]	25,541		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	[7]	7,761		8,060
FICO Score 700 and Above [Member] | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7]	137		151
FICO Score 700 and Above [Member] | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		9,990		9,642
FICO Score 700 and Above [Member] | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		10,008		9,315
FICO Score 700 and Above [Member] | Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,101		1,142
FICO Score Between 620 and 699 | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7]	2,288		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	[7]	1,003		1,015
FICO Score Between 620 and 699 | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7]	24		27
FICO Score Between 620 and 699 | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		996		935
FICO Score Between 620 and 699 | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,449		2,395
FICO Score Between 620 and 699 | Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		411		420
FICO Score Below 620 | Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7],[10]	632		705
FICO Score Below 620 | Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7],[10]	403		393
FICO Score Below 620 | Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[7],[10]	6		6
FICO Score Below 620 | Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[10]	43		38
FICO Score Below 620 | Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[10]	811		709
FICO Score Below 620 | Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[10]	$ 125		$ 127

[1] Includes loans of consolidated VIEs of $147 million and $153 million at March 31, 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 $296 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 $4.1 billion of sales-type and direct financing leases at both March 31, 2019 and December 31, 2018, and $786 million and $796 million of installment loans at March 31, 2019 and December 31, 2018, respectively.

[6] Includes $134 million of LHFI measured at fair value, the majority of which were accruing current.

[7] Excludes $7.3 billion and $7.2 billion of guaranteed student loans and $467 million and $459 million of guaranteed residential mortgages at March 31, 2019 and December 31, 2018, respectively, for which there was nominal risk of principal loss due to the government guarantee.

[8] Includes $134 million and $163 million of LHFI measured at fair value at March 31, 2019 and December 31, 2018, respectively.

[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.