Investments in Partnerships - Summary of Equity Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Investments in real estate, at cost:
Operating properties	$ 1,147,457	$ 883,530
Construction in progress	35,940	251,029
Total investments in real estate	1,183,397	1,134,559
Accumulated depreciation	(256,471)	(229,877)
Net investments in real estate	926,926	904,682
Cash and cash equivalents	29,058	34,766
Deferred costs and other assets, net	117,609	43,476
Total assets	1,073,593	982,924
LIABILITIES AND PARTNERS’ INVESTMENT:
Mortgage loans payable, net	493,634	499,057
FDP Term Loan, net	299,575	299,091
Other liabilities	124,703	79,166
Total liabilities	917,912	877,314
Net investment	155,681	105,610
Partners’ share	76,128	50,997
PREIT’s share	79,553	54,613
Excess investment	18,669	17,464
Net investments and advances	98,222	72,077
Reconciliation to comparable GAAP balance sheet item:
Investment in partnerships, at equity	176,070	159,993
Distributions in excess of partnership investments	(77,848)	(87,916)
Net investment	$ 98,222	$ 72,077