Debt (Narratives) (Details) (USD $)	3 Months Ended							3 Months Ended
	Mar. 31, 2013	Mar. 31, 2013 Fixed Interest Rate Loans	Mar. 31, 2013 Variable Interest Rate Loans	Mar. 31, 2013 Domestic	Mar. 31, 2013 Revolving Credit Facility	Feb. 29, 2012 Revolving Credit Facility	Mar. 31, 2013 Term Loan Facility	Mar. 31, 2013 Senior Credit Facility
Revolving Line Of Credit
Senior credit facility					$ 450,000,000	$ 450,000,000	$ 175,000,000	$ 625,000,000
Credit facility, expiration date								Dec. 31, 2014
Credit facility, interest rate at end of period
Letters of credit outstanding amount								5,400,000
Credit facililty potential increase								125,000,000
Debt instrument, covenant compliance								We were in compliance with all of these covenants at March 31, 2013.
Line of credit facility, available								625,000,000
AmountOutstanding							175,000,000	298,000,000
Non Recourse Debt
Amount of debt acquired				36,500,000
Collateral mortgage loan, carrying value	2,000,000,000
Mortgage loan on real estate, minimum interest rate		2.70%	1.20%
Mortgage loan on real estate, maximum interest rate		10.00%	8.50%
Debt instrument maturity date, range start	Jan. 01, 2013
Debt instrument maturity date, range end	Dec. 31, 2026
Mortgage loans on real estate, interest rate	5.00%			4.05%
Debt refinanced	41,500,000
Debt refinanced, restated carrying value	$ 62,500,000
Mortgage loan term	10			10