Equity - Changes in Equity, Simon Property Group, Inc. (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($)
Increase (Decrease) in Stockholders' Equity
Balance	$ 4,238,764
Issuance of limited partner units	84,103
Treasury stock purchase	(307,296)
Redemption of limited partner units	(7,619)
LTIP Units	23,654
Cumulative effect of accounting change	7,264
Purchase and disposition of noncontrolling interests, net and other	(12,701)
Distributions to common shareholders and limited partners, excluding Operating Partnership preferred interests	(2,106,140)
Distributions to noncontrolling other interest holders	(1,020)
Comprehensive income, excluding $1,436 attributable to preferred interests in the Operating Partnership and a $379 loss attributable to noncontrolling redeemable interests in properties	1,978,492
Balance	3,897,501
Comprehensive income attributable to preferred interests	1,436
Comprehensive loss attributable to noncontrolling redeemable interests in properties	379
Preferred Stock
Increase (Decrease) in Stockholders' Equity
Balance	43,077
Purchase and disposition of noncontrolling interests, net and other	(247)
Balance	42,830
Common Stock
Increase (Decrease) in Stockholders' Equity
Balance	32
Balance	32
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity
Balance	(110,453)
Comprehensive income, excluding $1,436 attributable to preferred interests in the Operating Partnership and a $379 loss attributable to noncontrolling redeemable interests in properties	(8,140)
Balance	(118,593)
Capital in Excess of Par Value
Increase (Decrease) in Stockholders' Equity
Balance	9,614,748
Exchange of limited partner units for common shares	1,004
Redemption of limited partner units	(7,047)
Purchase and disposition of noncontrolling interests, net and other	308
Adjustment to limited partners' interest from change in ownership in the Operating Partnership	127,707
Balance	9,736,720
Accumulated Deficit
Increase (Decrease) in Stockholders' Equity
Balance	(4,782,173)
Cumulative effect of accounting change	7,264
Purchase and disposition of noncontrolling interests, net and other	(18,663)
Distributions to common shareholders and limited partners, excluding Operating Partnership preferred interests	(1,829,610)
Comprehensive income, excluding $1,436 attributable to preferred interests in the Operating Partnership and a $379 loss attributable to noncontrolling redeemable interests in properties	1,726,428
Balance	(4,896,754)
Common Stock Held in Treasury
Increase (Decrease) in Stockholders' Equity
Balance	(1,079,063)
Treasury stock purchase	(307,296)
Purchase and disposition of noncontrolling interests, net and other	5,740
Balance	(1,380,619)
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity
Balance	552,596
Exchange of limited partner units for common shares	(1,004)
Issuance of limited partner units	84,103
Redemption of limited partner units	(572)
LTIP Units	23,654
Purchase and disposition of noncontrolling interests, net and other	161
Adjustment to limited partners' interest from change in ownership in the Operating Partnership	(127,707)
Distributions to common shareholders and limited partners, excluding Operating Partnership preferred interests	(276,530)
Distributions to noncontrolling other interest holders	(1,020)
Comprehensive income, excluding $1,436 attributable to preferred interests in the Operating Partnership and a $379 loss attributable to noncontrolling redeemable interests in properties	260,204
Balance	$ 513,885