Fair Value Measurements (Details) - SIMON PROPERTY GROUP AND ADOPTING ENTITIES MATCHING SAVINGS PLAN - USD ($)	Dec. 31, 2025	Dec. 31, 2024
Fair Value Measurements
Total assets at fair value	$ 668,939,754	$ 592,722,851
Level 1
Fair Value Measurements
Total assets at fair value	668,939,754	592,722,851
Common Stock
Fair Value Measurements
Total assets at fair value	35,292,847	33,957,609
Common Stock \| Level 1
Fair Value Measurements
Total assets at fair value	35,292,847	33,957,609
Common/collective trust funds
Fair Value Measurements
Total assets at fair value	633,646,907	558,765,242
Common/collective trust funds \| Level 1
Fair Value Measurements
Total assets at fair value	$ 633,646,907	$ 558,765,242

Fair value of investment, excluding plan interest in master trust, held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Includes, but is not limited to, derivative, investment measured at net asset value per share as practical expedient, and insurance contract not meeting fully-benefit responsive investment criteria.

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+ Details

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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