Commitments and Contingencies (Details Textuals) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies (Textuals) [Abstract]
Number of outstanding letters of credit	12
Outstanding letters of credit	$ 174,999
Additional financing to complete construction	493,972
Total contingent purchase obligations	29,127
Operating lease obligations relating to certain ground leases	1,105,992
Aggregate future minimum rentals to be received	74,744
Gross assets under capital lease recorded in real property	167,324
Outstanding construction financings for leased properties	506,091	$ 258,968
Accumulated Depreciation assets under capital lease recorded in real property	$ 24,929
Minimum part of economic life of leased asset to be classified as capital lease	75.00%
Minimum net present value of future minimum lease payments to be classified as capital lease	90.00%
Letter of credit expiration date maximum	Dec. 31, 2017
Letter of credit expiration date minimum	Dec. 31, 2024