Receivables Held for Sale - Receivables Sold to Third Party Investors (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Aggregate cash consideration received	$ 4,307	$ 0
Gain on sale of real estate secured receivables	617	$ 0
Real Estate Secured Receivables Held for Sale [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid principal balance at the time of sale	4,363
Aggregate cash consideration received	4,307
Aggregate carrying value at the time of sale	3,665
Transaction costs	25
Gain on sale of real estate secured receivables	$ 617