Indebtedness - Debt (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) item property	Dec. 31, 2018 USD ($)
Debt
Debt issuance costs	$ 101,280	$ 96,175
Other Debt Obligations	67,255	67,255
Total Mortgages and Unsecured Indebtedness	24,163,230	23,305,535
Fixed-Rate Debt:
Fixed rate debt	23,230,912	22,393,936
Net unamortized debt premium	6,775
Net discounts	54,976
Variable-Rate Debt:
Variable-rate mortgages and unsecured indebtedness	865,063	844,344
Simon Property Group, L.P.
Debt
Total Mortgages and Unsecured Indebtedness	24,163,230	23,305,535
Secured Debt | Mortgages
Debt
Total Mortgages and Unsecured Indebtedness	$ 6,900,000	6,800,000
Debt covenants
Number of non-recourse mortgage notes under which the Company and subsidiaries are borrowers | item	46
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	$ 15,195	14,522
Fixed-Rate Debt:
Fixed rate debt	6,156,595	6,099,787
Net unamortized debt premium	$ 6,775	11,822
Weighted average maturity period, fixed-rate debt	4 years 9 months 18 days
Secured Debt | Fixed Rate Mortgages | Weighted average
Fixed-Rate Debt:
Fixed rate of interest	3.87%
Secured Debt | Variable Rate Mortgages
Debt
Debt issuance costs	$ 4,721	5,901
Variable-Rate Debt:
Variable-rate mortgages and unsecured indebtedness	$ 751,130	736,274
Weighted average maturity period, variable-rate debt	2 years
Secured Debt | Variable Rate Mortgages | Weighted average
Variable-Rate Debt:
Variable rate of interest	2.62%
Unsecured Debt | Senior unsecured notes
Debt
Debt issuance costs	$ 70,297	58,822
Fixed-Rate Debt:
Fixed rate debt	15,747,267	15,535,468
Net discounts	$ 54,976	44,691
Weighted average maturity period, fixed-rate debt	9 years 3 months 18 days
Unsecured Debt | Senior unsecured notes | Simon Property Group, L.P.
Debt
Total Mortgages and Unsecured Indebtedness	$ 15,900,000
Unsecured Debt | Senior unsecured notes | Weighted average
Fixed-Rate Debt:
Fixed rate of interest	3.07%
Unsecured Debt | Commercial Paper
Fixed-Rate Debt:
Fixed rate debt	$ 1,327,050	758,681
Unsecured Debt | Commercial Paper | Simon Property Group, L.P.
Debt
Credit facility, amount outstanding	1,300,000
Maximum borrowing capacity	2,000,000
Unsecured Debt | Commercial Paper | Simon Property Group, L.P. | USD
Debt
Credit facility, amount outstanding	$ 1,000,000
Weighted average interest rate (as a percent)	1.72%
Unsecured Debt | Commercial Paper | Simon Property Group, L.P. | Euro
Debt
Credit facility, amount outstanding	$ 269,200
Weighted average interest rate (as a percent)	(0.38%)
Unsecured Debt | Credit Facility and the Supplemental Facility | Simon Property Group, L.P.
Debt
Available borrowing capacity	$ 6,000,000
Maximum amount outstanding during period	130,700
Credit facility, weighted average amount outstanding	125,100
Letters of credit outstanding	11,400
Unsecured Debt | Credit Facility
Debt
Debt issuance costs	11,067	16,930
Variable-Rate Debt:
Variable-rate mortgages and unsecured indebtedness	113,933	$ 108,070
Unsecured Debt | Credit Facility | Simon Property Group, L.P.
Debt
Credit facility, amount outstanding	125,000
Maximum borrowing capacity	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%
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
Maximum borrowing capacity	$ 3,500,000
Optional expanded maximum borrowing capacity	$ 4,500,000
Additional facility fee (as a percent)	0.10%
Unsecured Debt | Supplemental Facility | Simon Property Group, L.P. | LIBOR
Debt
Interest added to reference rate (as a percent)	0.775%