Identified Intangible Assets and Liabilities (Schedule of Identified Intangible Assets and Intangible Liabilities) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Gross amount	$ 121,313	$ 129,552
Accumulated amortization	(95,567)	(98,587)
Total, net	25,746	30,965
Identified intangible liabilities (included in deferred revenue):
Gross amount	292,730	316,119
Accumulated amortization	(252,554)	(262,580)
Total, net	$ 40,176	$ 53,539