Real Estate Investments and Related Intangibles - Consolidated Joint Ventures Narrative (Details)	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2021 USD ($) property	Sep. 30, 2021 USD ($) jointVenture property	Dec. 31, 2020 USD ($) jointVenture property
Schedule of Equity Method Investments [Line Items]
Number of Properties | property	3,882	3,882
Total assets	$ 12,578,893,000	$ 12,578,893,000	$ 13,355,056,000
Real estate investments, net	10,555,653,000	10,555,653,000	10,770,542,000
Mortgages [Member]
Schedule of Equity Method Investments [Line Items]
Aggregate balance outstanding	991,803,000	991,803,000	$ 1,333,195,000
Debt repayments		$ 341,392,000
Joint ventures [Member]
Schedule of Equity Method Investments [Line Items]
Number of joint ventures | jointVenture		1	1
Total assets	30,700,000	$ 30,700,000	$ 33,000,000
Real estate investments, net	$ 27,800,000	$ 27,800,000	$ 29,100,000
Joint ventures [Member] | Consolidated Properties [Member]
Schedule of Equity Method Investments [Line Items]
Number of Properties | property	1	1	1
Joint ventures [Member] | Consolidated Properties [Member] | Mortgages [Member]
Schedule of Equity Method Investments [Line Items]
Aggregate balance outstanding	$ 0	$ 0	$ 14,800,000
Debt repayments	$ 14,800,000