Intangibles - Amortization of Deferred Leasing Costs and Acquisition Related Intangibles (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Intangibles
Depreciation and amortization expense related to amortization of lease-up intangibles	$ 76,732	$ 84,487	$ 74,978
Rental and related revenues related to amortization of net below market lease liabilities	2,030	3,877	3,781
Operating expense related to amortization of net below market ground lease intangibles	$ 740	$ 664	$ 664