Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount, after tax, of accumulated gain (loss) on derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=114867106&loc=d3e637-108580

+ Details

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

- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611

+ Details

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

- Definition

Fixed interest rate related to the interest rate derivative.

+ References

No definition available.

+ Details

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

- Definition

Fixed interest rate that will be received or paid upon exercise of the interest rate swaption contract.

+ References

No definition available.

+ Details

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

- Definition

Fair value as of the balance sheet date of all derivatives designated as foreign currency fair value hedging instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

+ Details

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

- Definition

Fair value as of the balance sheet date of interest rate derivative assets, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as assets.

+ References

No definition available.

+ Details

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

- 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

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 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Number of credit risk derivative instruments held.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

+ Details

Name:	us-gaap_NumberOfCreditRiskDerivativesHeld
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of interest rate derivative instruments held by the entity at the reporting date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

+ Details

Name:	us-gaap_NumberOfInterestRateDerivativesHeld
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
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=109223946&loc=d3e3291-108585

+ Details

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

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_DesignatedAsHedgingInstrumentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=spg_USDEuroForwardContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	spg_MaturityDateAxis=spg_CurrencyForwardContractsThatMaturesOnNovember2018Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	spg_MaturityDateAxis=spg_CurrencyForwardContractsMaturityMay152019TwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	spg_MaturityDateAxis=spg_CurrencyForwardContractsMaturityMay152020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	spg_MaturityDateAxis=spg_CurrencyForwardContractsMaturityMay142021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=spg_UsDenominatedCrossCurrencySwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_NetInvestmentHedgingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=spg_YenDenominatedCrossCurrencySwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_OtherLiabilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=spg_EuroDenominatedCrossCurrencySwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=spg_DeferredCostsAndOtherAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=spg_SimonPropertyGroupLimitedPartnershipMember
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_LongtermDebtTypeAxis=us-gaap_UnsecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CurrencyAxis=currency_JPY
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Summary of Significant Accounting Policies - Derivative Financial Instruments (Details) € in Thousands, $ in Millions, ¥ in Billions		3 Months Ended
	Jul. 10, 2018 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 EUR (€) DerivativeInstrument	Dec. 31, 2018 USD ($) DerivativeInstrument	Sep. 30, 2018 JPY (¥)	Sep. 30, 2018 USD ($)	Mar. 31, 2018 EUR (€)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 EUR (€) DerivativeInstrument	Dec. 31, 2017 USD ($) DerivativeInstrument
Derivative Financial Instruments
Number of credit-risk-related hedging or derivative activities \| DerivativeInstrument			0	0
Gross accumulated other comprehensive income related to derivative activities				$ 37.9						$ 9.3
Interest rate swap \| Designated as Hedging Instrument
Derivative Financial Instruments
Number of Instruments \| DerivativeInstrument			0	0					0	0
USD-Euro currency forward contract \| Nov 9, 2019 \| Designated as Hedging Instrument
Derivative Financial Instruments
Notional Amount \| €									€ 50,000
Forward contract net, fair value										$ (2.4)
USD-Euro currency forward contract \| May 15, 2019 \| Designated as Hedging Instrument
Derivative Financial Instruments
Notional Amount \| €			€ 50,000						50,000
Forward contract net, fair value				$ (0.8)						(4.9)
USD-Euro currency forward contract \| May 15, 2020 \| Designated as Hedging Instrument
Derivative Financial Instruments
Notional Amount \| €			50,000						50,000
Forward contract net, fair value				(1.5)						(5.2)
USD-Euro currency forward contract \| May 14, 2021 \| Designated as Hedging Instrument
Derivative Financial Instruments
Notional Amount \| €			€ 50,000						€ 50,000
Forward contract net, fair value				(2.0)						$ (5.5)
US denominated cross currency swap \| Net Investment Hedging \| Designated as Hedging Instrument
Derivative Financial Instruments
Notional Amount						$ 200.1		$ 150.0
Swapping interest rate					4.38%	4.38%	4.38%	4.38%
Yen denominated cross currency swap \| Net Investment Hedging \| Designated as Hedging Instrument
Derivative Financial Instruments
Notional Amount \| ¥					¥ 22.3
Fixed exchange rate					1.19%	1.19%
Yen denominated cross currency swap \| Other liabilities \| Net Investment Hedging \| Designated as Hedging Instrument
Derivative Financial Instruments
Fair value of cross currency				1.9
Euro denominated cross currency swap \| Net Investment Hedging \| Designated as Hedging Instrument
Derivative Financial Instruments
Notional Amount \| €							€ 121,600
Fixed exchange rate							1.37%	1.37%
Euro denominated cross currency swap \| Deferred costs and other assets \| Net Investment Hedging \| Designated as Hedging Instrument
Derivative Financial Instruments
Interest rate derivative asset, fair value				10.9
Simon Property Group, L.P. \| Credit Facility \| Unsecured Debt
Derivative Financial Instruments
Maximum borrowing capacity				$ 4,000.0		$ 4,000.0
Simon Property Group, L.P. \| Yen \| Credit Facility \| Unsecured Debt
Derivative Financial Instruments
Debt repaid	$ 201.3	$ 201.3