Debt and Borrowing Arrangements (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2011	Dec. 31, 2010
Debt, Long-term and Short-term, Combined Amount
Debt	$ 5,697	$ 8,085
Total Vehicle Management Asset-Backed Debt [Member]
Debt, Long-term and Short-term, Combined Amount
Debt	3,015	3,066
Term notes, in amortization [Member]
Debt, Long-term and Short-term, Combined Amount
Debt	1,627	1,167
Weighted Average -Interest Rate	2.00%	2.20%
Term notes, in revolving period [Member]
Debt, Long-term and Short-term, Combined Amount
Debt	92	989
Weighted Average -Interest Rate	2.10%	2.00%
Variable-funding notes [Member]
Debt, Long-term and Short-term, Combined Amount
Debt	1,260	871
Weighted Average -Interest Rate	1.60%	1.90%
Other [Member]
Debt, Long-term and Short-term, Combined Amount
Debt	36	39
Weighted Average -Interest Rate	5.10%	5.10%
Total Mortgage Asset-Backed Debt [Member]
Debt, Long-term and Short-term, Combined Amount
Debt	1,428	3,777
Committed warehouse facilities [Member]
Debt, Long-term and Short-term, Combined Amount
Debt	1,352	2,419
Weighted Average -Interest Rate	2.00%	2.10%
Uncommitted warehouse facilities [Member]
Debt, Long-term and Short-term, Combined Amount
Debt	0	1,290
Weighted Average -Interest Rate		1.20%
Servicing advance facility [Member]
Debt, Long-term and Short-term, Combined Amount
Debt	76	68
Weighted Average -Interest Rate	2.70%	2.80%
Unsecured Debt [Member]
Debt, Long-term and Short-term, Combined Amount
Debt	1,228	1,212
Term Notes [Member]
Debt, Long-term and Short-term, Combined Amount
Debt	781	782
Weighted Average -Interest Rate	8.10%	8.10%
Convertible notes [Member]
Debt, Long-term and Short-term, Combined Amount
Debt	447	430
Weighted Average -Interest Rate	4.00%	4.00%
Credit facilities [Member]
Debt, Long-term and Short-term, Combined Amount
Debt	0	0
Mortgage loan securitization debt certificates [Member]
Debt, Long-term and Short-term, Combined Amount
Debt	$ 26	$ 30
Weighted Average -Interest Rate	7.00%	7.00%