Acquired Intangible Assets and Liabilities (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Amortization of acquired leases	$ (17,100)	$ (27,300)	$ (2,200)
Expected average remaining lives of acquired below market leases (in years)	8 years
Amortization of acquired in-place lease value and deferred leasing costs	$ 354,302	416,621	247,468
Acquired above-market leases
Finite-Lived Intangible Assets [Line Items]
Expected average remaining lives (in years)	2 years 6 months
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 acquired in-place lease value and deferred leasing costs	$ 143,000	211,000	101,200
Weighted average remaining contractual life for acquired leases excluding renewals or extensions (in years)	5 years 6 months
Tenant relationship value
Finite-Lived Intangible Assets [Line Items]
Amortization of acquired in-place lease value and deferred leasing costs	$ 128,400	$ 123,500	$ 85,900
Weighted average remaining contractual life for acquired leases excluding renewals or extensions (in years)	13 years