Investments in Partnerships - Summary of Equity Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Investments in real estate, at cost:
Operating properties	$ 844,214	$ 824,328
Construction in progress	7,786	20,632
Total investments in real estate	852,000	844,960
Accumulated depreciation	(240,713)	(224,641)
Net investments in real estate	611,287	620,319
Cash and cash equivalents	51,433	28,060
Deferred costs and other assets, net	163,575	161,465
Total assets	826,295	809,844
LIABILITIES AND PARTNERS’ INVESTMENT:
Mortgage loans payable, net	496,257	491,119
FDP Term Loan, net	194,603	201,000
Partnership Loan	109,897	100,000
Other liabilities	139,904	132,715
Total liabilities	940,661	924,834
Net investment	(114,366)	(114,990)
Partners’ share	(57,984)	(59,080)
PREIT’s share	(56,382)	(55,910)
Excess investment	6,702	6,390
Net investments and advances	(49,680)	(49,520)
Investment in partnerships, at equity	19,947	27,066
Distributions in excess of partnership investments	$ (69,627)	$ (76,586)