Composition of the Company's Loan Portfolio (Detail) - USD ($) $ in Millions		Jun. 30, 2018		Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[1]	$ 144,935		$ 143,181
Loans Held for Sale	[2]	2,283		2,290
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[3]	67,343		66,356
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		6,302		5,317
Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		3,456		3,804
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		77,101		75,477
Federal National Mortgage Association (FNMA) Insured Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		525		560
Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4],[5]	27,556	[6]	27,136	[7]
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	9,918		10,626
Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[4]	217		298
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		6,892		6,633
Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		9,448		8,729
Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		11,712		12,140
Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,566		1,582
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		$ 67,834		$ 67,704

[1] Includes loans of consolidated VIEs of $165 million and $179 million at June 30, 2018 and December 31, 2017, respectively.

[2] Includes $2.0 billion and $1.6 billion of LHFS measured at fair value at June 30, 2018 and December 31, 2017, respectively.

[3] Includes $3.8 billion and $3.7 billion of lease financing, and $800 million and $778 million of installment loans at June 30, 2018 and December 31, 2017, respectively.

[4] Excludes $6.9 billion and $6.6 billion of guaranteed student loans and $525 million and $560 million of guaranteed residential mortgages at June 30, 2018 and December 31, 2017, respectively, for which there was nominal risk of principal loss due to the government guarantee.

[5] Includes $177 million and $196 million of LHFI measured at fair value at June 30, 2018 and December 31, 2017, respectively.

[6] Includes nonaccruing LHFI past due 90 days or more of $363 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.2 Includes $177 million of loans measured at fair value, the majority of which were accruing current.

[7] 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.