Debt and Borrowing Arrangements (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2011	Dec. 31, 2010
Debt and Borrowing Arrangements
Total Debt	$ 6,561	$ 8,085
Vehicle Management Asset-Backed Debt
Debt and Borrowing Arrangements
Total Debt	2,933	3,066
Term notes, in amortization
Debt and Borrowing Arrangements
Total Debt	1,363	1,167
Weighted Avg-Interest Rate (as a percent)	2.10%	2.20%
Term notes, in revolving period
Debt and Borrowing Arrangements
Total Debt	426	989
Weighted Avg-Interest Rate (as a percent)	1.60%	2.00%
Variable-funding notes
Debt and Borrowing Arrangements
Total Debt	1,111	871
Weighted Avg-Interest Rate (as a percent)	1.40%	1.90%
Other.
Debt and Borrowing Arrangements
Total Debt	33	39
Weighted Avg-Interest Rate (as a percent)	5.10%	5.10%
Mortgage Asset-Backed Debt
Debt and Borrowing Arrangements
Total Debt	2,287	3,777
Committed warehouse facilities
Debt and Borrowing Arrangements
Total Debt	2,078	2,419
Weighted Avg-Interest Rate (as a percent)	1.90%	2.10%
Uncommitted warehouse facilities
Debt and Borrowing Arrangements
Total Debt	135	1,290
Weighted Avg-Interest Rate (as a percent)	1.20%	1.20%
Servicing advance facility
Debt and Borrowing Arrangements
Total Debt	74	68
Weighted Avg-Interest Rate (as a percent)	2.70%	2.80%
Unsecured Debt
Debt and Borrowing Arrangements
Total Debt	1,316	1,212
Term notes
Debt and Borrowing Arrangements
Total Debt	781	782
Weighted Avg-Interest Rate (as a percent)	8.10%	8.10%
Convertible notes
Debt and Borrowing Arrangements
Total Debt	455	430
Weighted Avg-Interest Rate (as a percent)	4.00%	4.00%
Unsecured Committed Credit Facilities
Debt and Borrowing Arrangements
Total Debt	80
Weighted Avg-Interest Rate (as a percent)	3.80%
Mortgage loan securitization debt certificates
Debt and Borrowing Arrangements
Total Debt	$ 25	$ 30
Weighted Avg-Interest Rate (as a percent)	7.00%	7.00%