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, 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)
Other Income.									398,476	370,582	296,978
Net income attributable to noncontrolling interests									(321,604)	(382,285)	(296,941)
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
Accumulated derivative losses, net, including noncontrolling interests | 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)
Accumulated derivative losses, attributable to noncontrolling interests | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
Net income attributable to noncontrolling interests									1,802	923	1,233
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)
Realized gains on sales of marketable securities, including Portion Attributable to Noncontrolling Interest | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
Other Income.											21,541
Realized gains on sales of marketable securities, attributable to Noncontrolling Interest | Amount reclassified from accumulated other comprehensive income (loss)
Significant Accounting Policies
Net income attributable to noncontrolling interests											(2,820)
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