No definition available.

Name:	spg_DebtCovenantsAbstract
Namespace Prefix:	spg_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt extension period.

+ References

No definition available.

+ Details

Name:	spg_DebtExtensionPeriod
Namespace Prefix:	spg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of additional percentage points added to the reference rate as a facility fee on the line of credit.

+ References

No definition available.

+ Details

Name:	spg_LineOfCreditAdditionalBasisSpreadOnVariableRate
Namespace Prefix:	spg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of maximum additional borrowing capacity.

+ References

No definition available.

+ Details

Name:	spg_LineOfCreditFacilityAdditionalBorrowingCapacityMaximum
Namespace Prefix:	spg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the percentage of other than borrowings in the currency of the country of domicile, identification of the currency in which borrowings are made.

+ References

No definition available.

+ Details

Name:	spg_LineOfCreditFacilityCurrencyPercentage
Namespace Prefix:	spg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity to which the credit facility may be expanded per the terms of the agreement, at the option of the reporting entity.

+ References

No definition available.

+ Details

Name:	spg_LineOfCreditFacilityMaximumBorrowingCapacityOptionalExpanded
Namespace Prefix:	spg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number of additional extension periods available under the credit facility.

+ References

No definition available.

+ Details

Name:	spg_NumberOfCreditFacilityExtensionPeriod
Namespace Prefix:	spg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of pools of cross-defaulted and cross-collateralized mortgages encumbering the entity's properties.

+ References

No definition available.

+ Details

Name:	spg_NumberOfCrossDefaultedAndCrossCollateralizedMortgagePoolsWithCollateralProperties
Namespace Prefix:	spg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The total number of properties pledged as collateral for cross defaulted and cross collateralized mortgages.

+ References

No definition available.

+ Details

Name:	spg_NumberOfPropertiesCrossDefaultedAndCrossCollateralizedMortgagesTotal
Namespace Prefix:	spg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of properties pledged as collateral to secure related mortgage notes.

+ References

No definition available.

+ Details

Name:	spg_NumberOfPropertiesPledgedAsCollateralToSecuredMortgageNotes
Namespace Prefix:	spg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of mortgage loans within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Footnote 3
-Subsection 29

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Footnote 3))
-URI http://asc.fasb.org/extlink&oid=120402547&loc=d3e617274-123014

+ Details

Name:	srt_MortgageLoansOnRealEstateNumberOfLoans
Namespace Prefix:	srt_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of the original debt instrument that was repurchased.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentRepurchasedFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=117329964&loc=d3e12355-112629

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=117329964&loc=d3e12317-112629

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

+ Details

Name:	us-gaap_GainsLossesOnExtinguishmentOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Average amount borrowed under the credit facility during the period.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityAverageOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum amount borrowed under the credit facility at any time during the period.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumAmountOutstandingDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3291-108585

+ Details

Name:	us-gaap_RepaymentsOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	dei_LegalEntityAxis=spg_SimonPropertyGroupLimitedPartnershipMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_MortgagesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_UnsecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=spg_SeniorUnsecuredNotesMaturingJuly2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=spg_SeniorUnsecuredNotesMaturingJanuary2028Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=spg_SeniorUnsecuredNotesMaturingJanuary2031Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=spg_SeniorUnsecuredNotes1.125DueMarch192033Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_CommercialPaperMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=spg_U.sDollarDenominatedNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=spg_CreditFacilityAndSupplementalFacilityAndTermFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=spg_CreditFacilityAndTermFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=spg_TermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_FederalFundsEffectiveSwapRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=spg_SupplementalRevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Indebtedness - Narrative (Details) $ in Thousands, € in Millions				3 Months Ended
	Mar. 23, 2021 USD ($)	Feb. 02, 2021 USD ($)	Jan. 27, 2021 USD ($)	Mar. 31, 2021 USD ($) item property	Mar. 19, 2021 USD ($)	Mar. 19, 2021 EUR (€)	Jan. 21, 2021 USD ($)	Dec. 31, 2020 USD ($)
Debt
Long-term debt				$ 26,156,520				$ 26,723,361
Loss on debt extinguishment				2,959
Simon Property Group, L.P.
Debt
Long-term debt				26,156,520				26,723,361
Loss on debt extinguishment				2,959
Secured Debt \| Mortgages
Debt
Long-term debt				$ 6,800,000				$ 7,000,000
Debt covenants
Number of non-recourse mortgage notes under which the Company and subsidiaries are borrowers \| item				46
Number of properties pledged as collateral \| property				49
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
Unsecured Debt \| Simon Property Group, L.P.
Debt
Maximum borrowing capacity				$ 3,500,000
Unsecured Debt \| Senior unsecured notes \| Simon Property Group, L.P.
Debt
Long-term debt				18,800,000
Unsecured Debt \| Senior Unsecured Notes 2.50% due 2021 \| Simon Property Group, L.P.
Debt
Amount of debt redeemed			$ 550,000
Interest rate on debt (as a percent)			2.50%
Loss on debt extinguishment			$ 3,000
Unsecured Debt \| Senior Unsecured Notes Maturing February 2028 \| Simon Property Group, L.P.
Debt
Debt issued							$ 800,000
Interest rate on debt (as a percent)							1.75%
Unsecured Debt \| Senior Unsecured Notes Maturing February 2031 \| Simon Property Group, L.P.
Debt
Debt issued							$ 700,000
Interest rate on debt (as a percent)							2.20%
Unsecured Debt \| Senior unsecured notes 1.125% due March 19,2033 \| Simon Property Group, L.P.
Debt
Debt issued					$ 893,000	€ 750
Interest rate on debt (as a percent)					1.125%	1.125%
Unsecured Debt \| Commercial Paper \| Simon Property Group, L.P.
Debt
Credit facility, amount outstanding				500,000
Maximum borrowing capacity				2,000,000
Unsecured Debt \| U.S Dollar Denominated Notes \| Simon Property Group, L.P.
Debt
Credit facility, amount outstanding				$ 500,000
Weighted average interest rate (as a percent)				0.22%
Unsecured Debt \| Facilities \| Simon Property Group, L.P.
Debt
Available borrowing capacity				$ 6,900,000
Maximum amount outstanding during period				2,100,000
Credit facility, weighted average amount outstanding				1,500,000
Letters of credit outstanding				12,400
Unsecured Debt \| Credit Facility and Term Facility \| Simon Property Group, L.P.
Debt
Maximum borrowing capacity				5,000,000
Additional borrowing capacity				$ 1,000,000
Additional extension period \| item				2
Debt extension period				6 months
Unsecured Debt \| Credit Facility and Term Facility \| Maximum \| Simon Property Group, L.P.
Debt
Percentage of borrowings in currencies other than the U.S. dollar				95.00%
Unsecured Debt \| Term loan \| Simon Property Group, L.P.
Debt
Maximum borrowing capacity				$ 2,000,000
Debt repaid	$ 1,250,000	$ 750,000
Unsecured Debt \| Credit Facility \| Simon Property Group, L.P.
Debt
Credit facility, amount outstanding				125,000
Maximum borrowing capacity				$ 4,000,000
Unsecured Debt \| Credit Facility \| Simon Property Group, L.P. \| LIBOR
Debt
Interest rate (as a percent)				1.00%
Unsecured Debt \| Credit Facility \| Simon Property Group, L.P. \| Fed Funds Effective Rate
Debt
Interest rate (as a percent)				0.50%
Unsecured Debt \| Credit Facility \| Minimum \| Simon Property Group, L.P. \| LIBOR
Debt
Interest rate (as a percent)				0.65%
Facility fee (in percentage)				0.10%
Unsecured Debt \| Credit Facility \| Minimum \| Simon Property Group, L.P. \| Base Rate
Debt
Interest rate (as a percent)				0.00%
Unsecured Debt \| Credit Facility \| Maximum \| Simon Property Group, L.P. \| LIBOR
Debt
Interest rate (as a percent)				1.40%
Facility fee (in percentage)				0.30%
Unsecured Debt \| Credit Facility \| Maximum \| Simon Property Group, L.P. \| Base Rate
Debt
Interest rate (as a percent)				0.40%
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 rate (as a percent)				0.775%