LHFI by Credit Quality Indicator (Additional Information) (Detail) - USD ($) $ in Millions		Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	[1]	$ 151,839	$ 143,181
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross		80,940	75,477
Federal National Mortgage Association (FNMA) Insured Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross		459	560
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross		$ 7,229	$ 6,600

[1] Includes loans of consolidated VIEs of $153 million and $179 million at December?31, 2018 and December?31, 2017, respectively.