Debt Mortgage Notes Payable (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Mortgage notes payable	$ 4,952,579	$ 5,086,515
Repayments Of Long-term Debt	126,500
Write Off Of Unamortized Deferred Financing Costs	100
Write off unamortized premium discount	$ 1,400
Debt Instrument, Maturity Date	May 01, 2061
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum	0.04%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum	7.25%
Weighted Average Mortgage Debt Interest Rate	4.20%
Credit enhanced debt [Member]
Debt Instrument [Line Items]
Mortgage notes payable	$ 700,500