Summary of Significant Accounting Policies - Reclassification Out of AOCI, Simon Property Group, Inc. (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Significant Accounting Policies
Other Income.									$ 208,254	$ 398,476	$ 370,582
Total accumulated other comprehensive income (loss)	$ (136,200)				$ (160,400)				(136,200)	(160,400)	(158,900)
Interest expense									(784,400)	(789,353)	(815,923)
Loss on extinguishment of debt										(116,256)
Net income attributable to noncontrolling interests									(164,760)	(321,604)	(382,285)
NET INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS	$ 271,483	$ 145,926	$ 254,213	$ 437,605	$ 510,194	$ 544,254	$ 495,324	$ 548,475	1,109,227	2,098,247	2,436,721
Currency translation adjustments, including noncontrolling interests | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
Other Income.									(1,739)
Currency translation adjustments, attributable to noncontrolling interests | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
Net income attributable to noncontrolling interests									219
Currency translation adjustments | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
NET INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS									(1,520)
Accumulated derivative losses, net, including noncontrolling interests | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
Interest expense									1,845	(2,782)	(7,020)
Loss on extinguishment of debt										(10,852)
Accumulated derivative losses, attributable to noncontrolling interests | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
Net income attributable to noncontrolling interests									(232)	1,802	923
Accumulated derivative gains (losses), net | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
NET INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS									$ 1,613	$ (11,832)	$ (6,097)