Real Estate Investments (Summary of Amortization Expense and Adjustments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Amortization of leases	$ 44,795	$ 54,439	$ 68,477
In-place leases, included in depreciation and amortization | In-place leases
Finite-Lived Intangible Assets [Line Items]
Amortization of leases	44,795	54,439	68,477
Total included in revenue from tenants
Finite-Lived Intangible Assets [Line Items]
Amortization (accretion) of leases	7,421	15,548	5,205
Total included in revenue from tenants | Above-market lease assets
Finite-Lived Intangible Assets [Line Items]
Amortization of leases	3,375	4,441	6,007
Total included in revenue from tenants | Below-market lease liabilities
Finite-Lived Intangible Assets [Line Items]
Amortization of leases	10,796	19,989	11,212
Total included in property operating expenses
Finite-Lived Intangible Assets [Line Items]
Amortization of leases	30	30	(30)
Total included in property operating expenses | Below-market ground lease asset
Finite-Lived Intangible Assets [Line Items]
Amortization of leases	32	32	(28)
Total included in property operating expenses | Above-market ground lease liability [1]
Finite-Lived Intangible Assets [Line Items]
Amortization of leases	$ 2	$ 2	$ 2