Investments in Unconsolidated Entities and International Investments - Unconsolidated Entity Transactions (Details) $ / shares in Units, $ in Thousands					1 Months Ended	3 Months Ended
	Dec. 29, 2020 USD ($) property $ / shares shares	Dec. 07, 2020 USD ($)	Feb. 19, 2020 USD ($) item	Sep. 15, 2016 item	Jan. 31, 2020 USD ($)	Mar. 31, 2021 USD ($) property	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Investment in Unconsolidated Entities
Payments for acquisitions						$ 56,250		$ 107,797
Income from unconsolidated entities						15,069		50,465
Total revenue						1,239,951		1,353,360
Operating Income						604,612		654,869
Consolidated net income						510,460		505,404
Simon Property Group, L.P.
Investment in Unconsolidated Entities
Payments for acquisitions						56,250		107,797
Income from unconsolidated entities						15,069		50,465
Total revenue						1,239,951		1,353,360
Operating Income						604,612		654,869
Consolidated net income						$ 510,460		$ 505,404
TRG
Investment in Unconsolidated Entities
Ownership interest (as a percent)	80.00%					80.00%
Share price (in dollars per share) | $ / shares	$ 43.00
Payments for acquisitions	$ 3,500,000
Income from unconsolidated entities						$ (24,800)
Total revenue						135,400
Operating Income						36,800
Consolidated net income						8,700
Aggregate investment in ventures						3,436,304			$ 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
Issuance of preferred units	$ 362,500
Preferred stock stated dividend rate (as a percent)	6.38%
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						$ 3,436,304			$ 3,451,897
TRG | TRG
Investment in Unconsolidated Entities
Number of regional, super regional and outlet malls | property	24					24
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
Aggregate investment in ventures			$ 67,600
Bargain purchase gain							$ 35,000
Number of joint ventures | item			2
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%
Payments for acquisitions					$ 6,700
Additional noncontrolling interest purchased					5.05%
Authentic Brands Group LLC
Investment in Unconsolidated Entities
Ownership interest (as a percent)						6.80%
Payments for acquisitions					$ 33,500
Additional noncontrolling interest purchased					1.37%