Receivables, net - Receivables and Receivables held for Sale (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Modifications, primarily interest rate modifications	$ 26	$ 40	$ 82	$ 100
Re-age of past due account	41	66	97	157
Total	67	106	179	257
First lien [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	15	17	33	142
Second lien [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	10	12	33	28
Real Estate Secured Receivables Held for Sale [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	42	77	113	87
Real estate secured [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 67	$ 106	$ 179	$ 257