Acquired Intangible Assets and Liabilities (Narrative) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Mar. 09, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Finite-Lived Intangible Assets [Line Items]
Amortization of customer relationship value, acquired in-place lease value and deferred leasing costs				$ 268,844	$ 276,088
Customer Relationship Value
Finite-Lived Intangible Assets [Line Items]
Expected average remaining lives (in years)	20 years
Amortization of customer relationship value, acquired in-place lease value and deferred leasing costs		$ 49,700	$ 30,700	$ 128,500	99,300
Weighted average remaining contractual life for acquired leases excluding renewals or extensions (in years)				14 years 10 months 24 days
Acquired in-place lease value
Finite-Lived Intangible Assets [Line Items]
Expected average remaining lives (in years)				5 years 9 months 18 days
Amortization of customer relationship value, acquired in-place lease value and deferred leasing costs		25,400	32,400	$ 82,400	114,700
Weighted average remaining contractual life for acquired leases excluding renewals or extensions (in years)				5 years 7 months 6 days
Below-Market Leases, Net of Above-Market Leases
Finite-Lived Intangible Assets [Line Items]
Amortization of acquired leases		$ 2,400	$ 2,800	$ 8,700	$ 13,000
Expected average remaining lives of acquired below market leases (in years)				7 years 4 months 24 days
Expected average remaining lives (in years)				2 years 2 months 12 days