Mortgage Notes Payable, Unsecured Notes and Credit Facility (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Notes Payable, Unsecured Notes and Credit Facility
Total notes payable and unsecured notes	$ 6,864,985	$ 6,481,291
Credit Facility	0	0
Total mortgage notes payable, unsecured notes and Credit Facility	6,864,985	6,481,291
Unsecured notes
Notes Payable, Unsecured Notes and Credit Facility
Fixed rate notes	4,050,000	3,575,000
Total notes payable and unsecured notes	4,350,000
Amount of debt discount	7,178	7,601
Deferred Finance Costs, Net	23,657	21,725
Term Loan
Notes Payable, Unsecured Notes and Credit Facility
Variable rate notes	300,000	300,000
Secured notes
Notes Payable, Unsecured Notes and Credit Facility
Fixed rate notes	1,605,764	1,561,109
Variable rate notes	909,221	1,045,182
Total notes payable and unsecured notes	2,226,147
Deferred Finance Costs, Net	11,860	14,703
Amount of debt premium	11,701	19,686
Credit Facility
Notes Payable, Unsecured Notes and Credit Facility
Credit Facility	$ 0	$ 0