Commitments and Contingencies (Details Textual) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) Number	Dec. 31, 2017 USD ($)
Commitments and Contingencies (Textual) [Abstract]
Number of outstanding letters of credit | Number	14
Letter of credit obligation	$ 158,969
Line Of Credit Facility [Line Items]
Outstanding construction financings for leased properties	180,984	$ 237,746
Additional financing to complete construction	392,710
Total contingent purchase obligations	$ 10,350
Minimum part of economic life of the leased asset to be classified as capital lease	75.00%
Minimum net present value of the future minimum lease payments to be classified as capital lease.	90.00%
Operating lease obligations relating to certain ground leases	$ 1,121,736
Operating Leases, Future Minimum Payments Due, Future Minimum Sublease Rentals	76,388
Capital Leases, Future Minimum Payments Due	$ 87,922
Letter Of Credit Expiration Date Maximum	Dec. 31, 2024
Letter Of Credit Expiration Date Minimum	Jan. 01, 2018