Borrowings (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum	4.20%
Repayments of Long-term Debt	$ 10,500,000	$ 1,511,100,000	$ 61,700,000
Notes Payable	4,887,300,000	4,887,300,000
Other Notes Payable	27,100,000	37,400,000
Long-term Debt, Fair Value Adjustment	298,500,000	606,600,000
Long-term Debt, Total	5,212,900,000	5,531,300,000
Long-term Debt, Current Maturities	(1,012,600,000)	(11,900,000)
Long-term debt	4,200,300,000	5,519,400,000
Description of Derivative Activity Volume Percent	65.00%
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	1,010,000,000
Long-term Debt, Maturities, Repayments of Principal in Year Two	9,500,000
Long-term Debt, Maturities, Repayments of Principal in Year Three	205,600,000
Long-term Debt, Maturities, Repayments of Principal in Year Four	1,000,000,000
Long-term Debt, Maturities, Repayments of Principal in Year Five	200,300,000
Line of Credit Facility, Remaining Borrowing Capacity	1,360,000,000
Line of Credit Facility, Collateral, Amount	1,200,000,000
Line of Credit Facility, Amount Outstanding	0
Interest Paid, Net	$ 139,700,000	$ 171,900,000	$ 167,400,000
Debt Instrument, Interest Rate, Effective Percentage	3.10%	3.20%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum	7.13%