Troubled Debt Restructures and Nonperforming Receivables - TDR Loans (Details) - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Modifications [Line Items]
Unpaid principal balance subject to reduction		$ 6	$ 271
Receivables Held For Sale [Member] | Real estate secured [Member]
Financing Receivable, Modifications [Line Items]
Carrying value		136	1,691
Unpaid principal balance	[1]	$ 168	$ 2,323

[1] At September 30, 2017 and December 31, 2016, the unpaid principal balance reflected above includes $6 million and $271 million, respectively, which have received a reduction in the unpaid principal balance as part of an account management action.