Equity - Temporary Equity (Details) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2026 USD ($) item shares	Dec. 31, 2025 USD ($) shares
Redeemable preferred stock
Limited partners' preferred interest in the Operating Partnership and noncontrolling redeemable interests	$ 268,936	$ 233,306
Simon Property Group, L.P.
Redeemable preferred stock
Limited partners' preferred interest in the Operating Partnership and noncontrolling redeemable interests	$ 268,936	233,306
7.5% Cumulative Redeemable Preferred Units
Redeemable preferred stock
Number of series of units classified into temporary equity \| item	1
Noncontrolling interests redeemable at amounts in excess of fair value	$ 0	0
Limited partners' preferred interest in the Operating Partnership and noncontrolling redeemable interests	$ 10,537	$ 10,537
Preferred stock stated dividend rate (as a percent)	7.50%	7.50%
Temporary equity, shares authorized \| shares	260,000	260,000
Temporary equity, shares issued \| shares	105,373	105,373
Temporary equity, shares outstanding \| shares	105,373	105,373
7.5% Cumulative Redeemable Preferred Units \| Simon Property Group, L.P.
Redeemable preferred stock
Number of series of units classified into temporary equity \| item	1
Limited partners' preferred interest in the Operating Partnership and noncontrolling redeemable interests	$ 10,537	$ 10,537
Preferred stock stated dividend rate (as a percent)	7.50%	7.50%
Temporary equity, shares authorized \| shares	260,000	260,000
Temporary equity, shares issued \| shares	105,373	105,373
Temporary equity, shares outstanding \| shares	105,373	105,373
Other noncontrolling redeemable interest
Redeemable preferred stock
Limited partners' preferred interest in the Operating Partnership and noncontrolling redeemable interests	$ 258,399	$ 222,769
Other noncontrolling redeemable interest \| Simon Property Group, L.P.
Redeemable preferred stock
Limited partners' preferred interest in the Operating Partnership and noncontrolling redeemable interests	$ 258,399	$ 222,769