Significant Accounting Policies - Reclassification Out Of AOCI, Simon Property Group, L.P. (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Significant Accounting Policies
Total accumulated other comprehensive income (loss)	$ (176,900)		$ (176,900)		$ (160,400)
Interest expense	(201,858)	$ (202,382)	(586,545)	$ (599,541)
Simon Property Group, L.P.
Significant Accounting Policies
Total accumulated other comprehensive income (loss)	(203,800)		(203,800)		$ (184,800)
Interest expense	(201,858)	(202,382)	(586,545)	(599,541)
Simon Property Group, L.P. | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
Interest expense	$ 477	$ (1,087)	$ 1,435	$ (3,261)