Identified Intangible Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Finite-Lived Intangible Assets and Liabilities
Gross amount	$ 309,896		$ 310,097
Accumulated amortization	(157,062)		(150,837)
Total, net	152,834		159,260
Gross amount	529,951		530,497
Accumulated amortization	(336,049)		(324,897)
Total, net	193,902		$ 205,600
Below Market Leases Net Of Above Market Leases
Finite-Lived Intangible Assets and Liabilities
Amortization of Intangible Assets	10,581	$ 11,116
2019	30,529
2020	22,246
2021	17,475
2022	14,292
2023	11,590
Other Identified Intangible Assets
Finite-Lived Intangible Assets and Liabilities
Amortization of Intangible Assets	4,876	6,981
2019	15,169
2020	11,961
2021	10,981
2022	9,426
2023	9,295
Tenant Under Ground Leases
Finite-Lived Intangible Assets and Liabilities
Amortization of Intangible Assets	437	$ 437
2019	1,747
2020	1,747
2021	1,747
2022	1,747
2023	$ 1,747