Composition of the Company's Loan Portfolio (Additional Information) (Detail) - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	[1]	$ 144,264	$ 143,298
Loans Receivable, Fair Value Disclosure		206	222
Loans Held-for-sale, Fair Value Disclosure		2,252	3,540
Finance Leases Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross		3,457	3,693
Installment Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross		764	729
Residential Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross		38,730	38,990
Loans Receivable, Fair Value Disclosure		$ 206	$ 222

[1] Includes loans of consolidated VIEs of $186 million and $211 million at September 30, 2017 and December 31, 2016, respectively.