Receivables Held for Sale - Receivables Sold to Third Party Investors (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Aggregate cash consideration received		$ 9,663		$ 2,022		$ 2,242
Gain on sale of real estate secured receivables		633		12		63
Real Estate Secured Receivables Held for Sale [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid principal balance at the time of sale	$ 4,478	10,130	[1]	2,591	[1]	2,927	[1]
Aggregate cash consideration received		9,663		2,022		2,242
Aggregate carrying value at the time of sale	$ 4,040	8,973	[1]	1,995	[1]	2,152	[1]
Transaction costs		57		15		27
Gain on sale of real estate secured receivables		$ 633		$ 12		$ 63

[1] For the year ended December 31, 2016, amount includes receivables with an unpaid principal balance of $4,478 million (aggregate carrying value of $4,040 million) that were sold during the fourth quarter of 2016.