Summary of Significant Accounting Policies - Reclassification Out Of AOCI, Simon Property Group, L.P. (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Significant Accounting Policies
Cumulative translation adjustments	$ (160,400)				$ (158,900)				$ (160,400)	$ (158,900)
Interest expense									(789,353)	(815,923)	$ (809,393)
Loss on extinguishment of debt									(116,256)		(128,618)
NET INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS	510,194	$ 544,254	$ 495,324	$ 548,475	712,796	$ 556,267	$ 547,004	$ 620,654	2,098,247	2,436,721	1,944,625
Other Income.									398,476	370,582	296,978
Simon Property Group, L.P.
Significant Accounting Policies
Cumulative translation adjustments	(184,800)				(183,000)				(184,800)	(183,000)
Interest expense									(789,353)	(815,923)	(809,393)
Loss on extinguishment of debt									(116,256)		(128,618)
NET INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS	$ 587,931	$ 627,074	$ 570,389	$ 631,551	$ 821,237	$ 640,402	$ 629,822	$ 714,303	2,416,945	2,805,764	2,239,638
Other Income.									398,476	370,582	296,978
Accumulated derivative gains (losses), net | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
NET INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS									(11,832)	(6,097)	(8,186)
Accumulated derivative gains (losses), net | Simon Property Group, L.P. | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
Interest expense									(2,782)	(7,020)	(9,419)
Loss on extinguishment of debt									(10,852)
NET INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS									$ (13,634)	$ (7,020)	(9,419)
Net unrealized (losses) gains on marketable securities | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
NET INCOME ATTRIBUTABLE TO COMMON STOCKHOLDERS											18,721
Net unrealized (losses) gains on marketable securities | Simon Property Group, L.P. | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
Other Income.											$ 21,541