Identified Intangible Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets and Liabilities
Gross amount	$ 308,895	$ 310,097
Accumulated amortization	(172,114)	(150,837)
Net	136,781	159,260
Gross amount	503,373	530,497
Accumulated amortization	(341,779)	(324,897)
Net	161,594	205,600
Below Market Leases Net Of Above Market Leases
Finite-Lived Intangible Assets and Liabilities
Increase to rental income	38,573	46,103	$ 51,849
2019	24,661
2020	23,591
2021	18,857
2022	15,746
2023	13,215
Other Identified Intangible Assets
Finite-Lived Intangible Assets and Liabilities
Amortization of intangible assets	18,018	25,057	28,897
2019	13,726
2020	13,513
2021	11,974
2022	10,244
2023	10,157
Tenant Under Ground Leases
Finite-Lived Intangible Assets and Liabilities
Amortization of intangible assets		$ 1,747	$ 1,747
Increase to rent expense	1,747
2019	1,747
2020	1,747
2021	1,747
2022	1,747
2023	$ 1,747