Identified Intangible Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets and Liabilities
Gross amount	$ 310,097	$ 384,090
Accumulated amortization	(150,837)	(194,422)
Net	159,260	189,668
Gross amount	530,497	550,454
Accumulated amortization	(324,897)	(298,238)
Net	205,600	252,216
Below Market Leases Net Of Above Market Leases
Finite-Lived Intangible Assets and Liabilities
Amortization of intangible assets	46,103	51,849	$ 75,952
2018	41,969
2019	30,543
2020	22,260
2021	17,489
2022	14,306
Other Identified Intangible Assets
Finite-Lived Intangible Assets and Liabilities
Amortization of intangible assets	25,057	28,897	34,995
2018	19,449
2019	15,169
2020	11,960
2021	10,981
2022	9,425
Tenant Under Ground Leases
Finite-Lived Intangible Assets and Liabilities
Amortization of intangible assets	1,747	$ 1,747	$ 1,747
2018	1,747
2019	1,747
2020	1,747
2021	1,747
2022	$ 1,747