Summary of Significant Accounting Policies Deferred Leasing and Other Costs (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred Leasing and Other [Abstract]
Deferred leasing costs	$ 359,646,000	$ 333,706,000
Acquired lease-related intangible assets	174,241,000	190,595,000
Deferred Leasing Costs and Finite Lived Intangible Assets Acquired, gross	533,887,000	524,301,000
Accumulated amortization - deferred leasing costs	(120,756,000)	(109,843,000)
Accumulated amortization - acquired lease-related intangible assets	(83,366,000)	(94,014,000)
Deferred Leasing and other costs, net of accumulated amortization	329,765,000	320,444,000
Amortization of Intangible Assets	19,500,000	22,000,000.0	$ 25,000,000.0
Amortization of above market lease, charge to rental income	639,000	$ 703,000	$ 777,000
2021	18,925,000
2022	15,412,000
2023	13,603,000
2024	11,014,000
2025	8,866,000
Thereafter	21,927,000
Finite-Lived Intangible Assets, Net	(89,747,000)
2021	363,000
2022	353,000
2023	353,000
2024	59,000
2025	0
Thereafter	0
Net Charge to Rental Income	$ 1,128,000