Composition of the Company's Loan Portfolio (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
Loans Held for Sale	[2]	1,781		1,468
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[3]	73,278		71,137
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		7,889		7,265
Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		2,562		2,538
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		83,729		80,940
Federal National Mortgage Association (FNMA) Insured Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		467		459
Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[5],[6]	28,461	[4]	28,836	[7]
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[5]	9,167		9,468
Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment	[5]	167		184
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		7,300		7,200
Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		11,029		10,615
Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		13,268		12,419
Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		1,637		1,689
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for investment		$ 71,504		$ 70,899

[1] Includes loans of consolidated VIEs of $147 million and $153 million at March 31, 2019 and December 31, 2018, respectively.

[2] Includes $1.1 billion and $1.2 billion of LHFS measured at fair value at March 31, 2019 and December 31, 2018, respectively.

[3] 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.

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

[5] 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.

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

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