Corporate Indebtedness - Schedule of Consolidated Interest Expense, Excluding Capitalized Interest (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest expense
Interest expense before capitalized interest	$ 284,649	$ 348,062	$ 357,926
Interest capitalized	(26,020)	(24,067)	(31,108)
Interest income	(1,584)	(2,796)	(2,948)
Interest expense, net	$ 257,045	$ 321,199	$ 323,870