Debt (Debt With A Contractual Term Greater Than One Year) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Debt Instrument [Line Items]
Unsecured commercial paper	$ 35,800,000	$ 102,100,000
Credit facilities	159,794,000	213,772,000
Gross long-term debt	4,884,133,000	5,271,884,000
Less: current portion of long-term debt	(1,040,247,000)	(751,293,000)
Long-term debt	3,843,886,000	4,520,591,000
Long-term debt held by variable interest entities	1,447,015,000	2,003,941,000
5.25% Medium-Term Notes Due In 2012 ($400.0 Million Par Value) [Member]
Debt Instrument [Line Items]
Unsecured notes	399,916,000	399,825,000
Stated percentage of debt instrument	5.25%
Maturity date of debt instrument	2012
Par value of debt instrument	400,000,000
5.75% Medium-Term Notes Due In 2014 ($500.0 Million Par Value) [Member]
Debt Instrument [Line Items]
Unsecured notes	499,544,000	499,383,000
Stated percentage of debt instrument	5.75%
Maturity date of debt instrument	2014
Par value of debt instrument	500,000,000
3.75% Medium-term notes Due In 2016 ($450.0 Million Par Value) [Member]
Debt Instrument [Line Items]
Unsecured notes	449,775,000
Stated percentage of debt instrument	3.75%
Maturity date of debt instrument	2016
Par value of debt instrument	450,000,000
6.80% Medium-Term Notes Due In 2018 ($950.1 Million Par Value) [Member]
Debt Instrument [Line Items]
Unsecured notes	948,958,000	998,570,000
Stated percentage of debt instrument	6.80%
Maturity date of debt instrument	2018
Par value of debt instrument	950,100,000
15.00% Senior Unsecured Notes Due In 2014 ($600.0 Million Par Value) [Member]
Debt Instrument [Line Items]
Unsecured notes	303,000,000	303,000,000
Stated percentage of debt instrument	15.00%
Maturity date of debt instrument	2014
Par value of debt instrument	600,000,000
Term Asset-Backed Securitization Debt [Member]
Debt Instrument [Line Items]
Gross long-term debt	$ 2,087,346,000	$ 2,755,234,000