LHFI by Credit Quality Indicator (Additional Information) (Detail) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	[1]	$ 143,298	$ 136,442
Federal National Mortgage Association (FNMA) Insured Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross		537	629
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross		$ 6,167	$ 4,922

[1] Includes loans of consolidated VIEs of $211 million and $246 million at December 31, 2016 and December 31, 2015, respectively.