Investments in Unconsolidated Entities and International Investments - Unconsolidated Entity Transactions (Details) $ / shares in Units, $ in Thousands						1 Months Ended	3 Months Ended					9 Months Ended
	Jun. 01, 2021 USD ($)	Dec. 29, 2020 USD ($) property $ / shares shares	Dec. 07, 2020 USD ($)	Feb. 19, 2020 USD ($) item	Sep. 15, 2016 item	Jan. 31, 2020 USD ($)	Sep. 30, 2021 USD ($) property	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Sep. 30, 2020 USD ($) item	Jun. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) property	Sep. 30, 2020 USD ($)	Jul. 01, 2021	Dec. 31, 2020 USD ($)
Investment in Unconsolidated Entities
Payments for acquisitions												$ 157,080	$ 107,797
Impairment charge to reduce investment to its estimated fair value										$ 55,200
Income from unconsolidated entities							$ 198,524			61,823		562,138	156,610
Total revenue							1,296,554			1,060,674		3,790,652	3,476,074
Operating Income							612,324			404,024		1,821,658	1,509,761
Consolidated net income							778,648			$ 168,646		1,994,977	964,598
Gain on exchange of equity interests							159,828					159,828
Number of joint ventures with recorded other-than-temporary impairment | item										3
Simon Property Group, L.P.
Investment in Unconsolidated Entities
Payments for acquisitions												157,080	107,797
Income from unconsolidated entities							198,524			$ 61,823		562,138	156,610
Total revenue							1,296,554			1,060,674		3,790,652	3,476,074
Operating Income							612,324			404,024		1,821,658	1,509,761
Consolidated net income							778,648			168,646		1,994,977	$ 964,598
Gain on exchange of equity interests							$ 159,828					$ 159,828
TRG
Investment in Unconsolidated Entities
Ownership interest (as a percent)		80.00%					80.00%					80.00%
Share price (in dollars per share) | $ / shares		$ 43.00
Payments for acquisitions		$ 3,500,000
Impairment charge to reduce investment to its estimated fair value							$ 31,600					$ 94,700
Income from unconsolidated entities							(11,500)					(49,900)
Total revenue												422,800
Operating Income												137,300
Consolidated net income												55,300
Aggregate investment in ventures							3,396,169					3,396,169			$ 3,451,897
TRG | Series J Cumulative Preferred Shares
Investment in Unconsolidated Entities
Redemption of preferred shares		$ 192,500
Preferred stock stated dividend rate (as a percent)		6.50%
TRG | Series K Cumulative Preferred Shares
Investment in Unconsolidated Entities
Redemption of preferred shares		$ 170,000
Preferred stock stated dividend rate (as a percent)		6.25%
TRG | Series A Cumulative Preferred Shares
Investment in Unconsolidated Entities
Preferred stock stated dividend rate (as a percent)		6.38%
Issuance of preferred units		$ 362,500
TRG | Simon Property Group, L.P.
Investment in Unconsolidated Entities
Number of units issued in connection with acquisition | shares		955,705
Aggregate investment in ventures							$ 3,396,169					$ 3,396,169			$ 3,451,897
TRG | TRG
Investment in Unconsolidated Entities
Number of regional, super regional and outlet malls | property		24					24					24
Eddie Bauer
Investment in Unconsolidated Entities
Ownership interest (as a percent)	49.00%
Payments for acquisitions	$ 100,800
J.C. Penny Department Store
Investment in Unconsolidated Entities
Ownership interest (as a percent)			41.67%
Payments for acquisitions			$ 125,000
Forever 21
Investment in Unconsolidated Entities
Ownership interest (as a percent)									50.00%
Payments for acquisitions									$ 56,300
Number of joint ventures | item				2
Aggregate investment in ventures				$ 67,600
Bargain purchase gain											$ 35,000
Additional noncontrolling interest purchased									12.50%
SPARC Group
Investment in Unconsolidated Entities
Number of joint ventures | item					2
SPARC Group Retail Operations
Investment in Unconsolidated Entities
Ownership interest (as a percent)							50.00%					50.00%
Payments for acquisitions						$ 6,700
Additional noncontrolling interest purchased						5.05%
Authentic Brands Group LLC
Investment in Unconsolidated Entities
Payments for acquisitions						$ 33,500
Additional noncontrolling interest purchased						1.37%
ABG
Investment in Unconsolidated Entities
Ownership interest (as a percent)														11.00%
Gain on exchange of equity interests							$ 159,800
Deferred Taxes							$ 47,900
HBS
Investment in Unconsolidated Entities
Impairment charge to reduce investment to its estimated fair value										$ 36,100
Multi family residential property
Investment in Unconsolidated Entities
Proceeds from sale or disposal of real estate assets								$ 27,100
Gain (loss) on disposition of interest in properties								$ 14,900