Finance Receivables, Net, Sale of Finance Receivables (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended		12 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net carrying value (NCV) sold						$ 676	$ 682
Allowance included in NCV						17	18
Cash proceeds received						635	630
Beneficial interests received						$ 86	$ 101
Finance receivables sold and derecognized principal value		$ 301		$ 301				$ 549
Finance receivables sold and derecognized sales value		323		$ 323				596
Finance Receivable Beneficial Interest Weighted Average Life				2 years
Impact from prior sales of finance receivables	[1]	(79)	$ (125)	$ (273)	$ (411)
Collections on beneficial interest		10	20	37	62
Estimated Decrease to Operating Cash Flows		(67)	(102)	(228)	(337)
Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Collections on beneficial interest		12	$ 23	45	$ 74
Other Current Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beneficial Interest, Interest in Other Current Assets		46		46				77
Other Noncurrent Assets [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beneficial interest from sale of finance receivables		$ 37		$ 37				$ 64

[1] Represents cash that would have been collected had we not sold finance receivables.