Summary of Significant Accounting Policies and Procedures and Newly Adopted Accounting Standards - Provision For Impairment (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) property	Dec. 31, 2019 USD ($) property	Dec. 31, 2018 USD ($) property	Sep. 30, 2020 USD ($)
Provisions for Impairment
Number of properties owned	6,592
Provisions for impairment | $	$ 147,232	$ 40,186	$ 26,269
Number of impaired properties held for sale	6	1	0
Number of impaired properties held for investment	42	5	3
Number of impaired properties sold	51	45	41
Value of properties | $	$ 14,696,712	$ 13,833,882
Held for sale
Provisions for Impairment
Number of properties owned	21
COVID-19 impacted properties
Provisions for Impairment
Provisions for impairment | $	$ 105,000
Number of impaired properties held for investment	38
COVID-19 impacted properties | Theaters
Provisions for Impairment
Provisions for impairment | $	$ 83,800
Number of impaired properties held for investment	13
Value of properties | $	$ 39,600			$ 123,400
Other properties
Provisions for Impairment
Provisions for impairment | $	$ 42,200