Fair Value Measurements (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Estimated fair value of mortgages payable	$ 1,675,296	$ 1,689,668	$ 1,765,519	$ 1,840,294
Mortgages carrying value	1,570,383	1,608,516	1,644,657	1,678,660
Unamortized deferred financing costs	$ 71,777	$ 87,509	$ 103,241	$ 118,974
Market interest rate	4.34%	4.93%	4.62%	4.41%
Mortgage maturity term	4 years 292 days	5 years 292 days	6 years 292 days	7 years 292 days