Indebtedness and Derivative Financial Instruments (Details) $ in Thousands				3 Months Ended	12 Months Ended
	Feb. 15, 2018 USD ($)	Mar. 17, 2017 USD ($)	Mar. 16, 2017	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) property item	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jan. 03, 2018 USD ($)	Dec. 11, 2017 USD ($)	Jun. 01, 2017 USD ($)	Apr. 21, 2017 USD ($)
Debt
Debt issuance costs					$ 110,734	$ 97,836
Other Debt Obligations					68,420
Total Mortgages and Unsecured Indebtedness					24,632,463	22,977,104
Loss on debt extinguishment					128,618	136,777	$ 120,953
Fixed-Rate Debt:
Fixed-rate mortgages and unsecured indebtedness					23,374,732	22,083,330
Variable-Rate Debt:
Variable-rate mortgages and unsecured indebtedness					1,189,311	893,774
Simon Property Group, L.P.
Debt
Total Mortgages and Unsecured Indebtedness					24,632,463	22,977,104
Loss on debt extinguishment					128,618	136,777	$ 120,953
Secured Debt | Mortgages
Debt
Total Mortgages and Unsecured Indebtedness					$ 6,900,000	6,500,000
Debt covenants
Number of non-recourse mortgage notes under which the Company and subsidiaries are borrowers | item					47
Number of properties owned | property					50
Number of cross-defaulted and cross-collateralized mortgage pools | item					2
Total number of properties pledged as collateral for cross defaulted and cross collateralized mortgages | property					5
Secured Debt | Fixed Rate Mortgages
Debt
Debt issuance costs					$ 16,106	15,965
Fixed-Rate Debt:
Fixed-rate mortgages and unsecured indebtedness					6,020,552	5,876,831
Net premiums					$ 16,869	21,916
Weighted-average interest rate, fixed-rate debt (as a percent)					4.04%
Weighted average maturity period, fixed-rate debt					6 years 4 months 24 days
Secured Debt | Variable Rate Mortgages
Debt
Debt issuance costs					$ 8,988	690
Variable-Rate Debt:
Variable-rate mortgages and unsecured indebtedness					$ 883,781	592,655
Weighted average interest rate, variable-rate debt (as a percent)					2.49%
Weighted average maturity period, variable-rate debt					3 years 10 months 24 days
Unsecured Debt | Senior unsecured notes
Debt
Debt issuance costs					$ 68,535	65,801
Fixed-Rate Debt:
Fixed-rate mortgages and unsecured indebtedness					16,375,713	15,252,834
Net discounts					$ 51,657	46,426
Weighted-average interest rate, fixed-rate debt (as a percent)					3.16%
Weighted average maturity period, fixed-rate debt					7 years 9 months 18 days
Unsecured Debt | Senior unsecured notes | Simon Property Group, L.P.
Debt
Total Mortgages and Unsecured Indebtedness					$ 16,500,000
Unsecured Debt | Senior Unsecured Notes 2.63% due 2022 | Simon Property Group, L.P.
Debt
Debt issued										$ 600,000
Interest rate on debt (as a percent)										2.63%
Unsecured Debt | Senior Unsecured Notes 3.38% due 2027 | Simon Property Group, L.P.
Debt
Debt issued									$ 750,000	$ 750,000
Interest rate on debt (as a percent)									3.38%	3.38%
Unsecured Debt | Senior Unsecured Notes 2.75% due 2023 | Simon Property Group, L.P.
Debt
Debt issued									$ 600,000
Interest rate on debt (as a percent)									2.75%
Unsecured Debt | Senior Unsecured Notes 1.50% due 2018 | Simon Property Group, L.P.
Debt
Amount of debt redeemed								$ 750,000
Interest rate on debt (as a percent)								1.50%
Unsecured Debt | Senior Unsecured Note 2.15% | Simon Property Group, L.P.
Debt
Amount of debt redeemed					$ 600,000
Interest rate on debt (as a percent)					2.15%
Unsecured Debt | Senior Unsecured Note 5.65% | Simon Property Group, L.P.
Debt
Amount of debt redeemed					$ 1,250,000
Interest rate on debt (as a percent)					5.65%
Loss on debt extinguishment				$ 128,600
Unsecured Debt | Commercial Paper
Fixed-Rate Debt:
Fixed-rate mortgages and unsecured indebtedness					$ 978,467	953,665
Unsecured Debt | Commercial Paper | Simon Property Group, L.P.
Debt
Credit facility, amount outstanding					978,500
Maximum borrowing capacity					$ 1,000,000
Unsecured Debt | Commercial Paper | Simon Property Group, L.P. | USD
Debt
Weighted average interest rate (as a percent)					1.40%
Unsecured Debt | Credit Facility and the Supplemental Facility | Simon Property Group, L.P.
Debt
Available borrowing capacity					$ 6,200,000
Maximum amount outstanding during period					960,900
Credit facility, weighted average amount outstanding					455,500
Letters of credit outstanding					20,900
Unsecured Debt | Credit Facility
Debt
Debt issuance costs					17,106	15,380
Variable-Rate Debt:
Variable-rate mortgages and unsecured indebtedness					305,530	$ 301,119
Unsecured Debt | Credit Facility | Simon Property Group, L.P.
Debt
Maximum borrowing capacity		$ 4,000,000			4,000,000
Optional expanded maximum borrowing capacity		$ 5,000,000
Additional facility fee (as a percent)		0.10%
Unsecured Debt | Credit Facility | Simon Property Group, L.P. | LIBOR
Debt
Interest added to reference rate (as a percent)		0.775%	0.80%
Unsecured Debt | Credit Facility | Simon Property Group, L.P. | Yen
Debt
Credit facility, amount outstanding					197,600
Unsecured Debt | Credit Facility | Maximum | Simon Property Group, L.P.
Debt
Percentage of borrowings in currencies other than the U.S. dollar		95.00%
Unsecured Debt | Supplemental Facility | Simon Property Group, L.P.
Debt
Credit facility, amount outstanding					322,600
Maximum borrowing capacity					$ 3,500,000
Interest added to reference rate (as a percent)	0.775%				0.80%
Additional facility fee (as a percent)	0.10%				0.10%
Expanded maximum borrowing capacity	$ 4,500,000				$ 4,250,000
Unsecured Debt | Supplemental Facility | Simon Property Group, L.P. | LIBOR
Debt
Interest added to reference rate (as a percent)					0.80%
Outlet Center In Roosendaal | European Joint Venture
Debt
Mortgage debt assumed											$ 40,100