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

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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-Topic 220
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Fair value of the assets less the liabilities of a derivative or group of derivatives.

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Fixed interest rate related to the interest rate derivative.

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

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

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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.

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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.

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Number of credit risk derivative instruments held.

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

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

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Summary of Significant Accounting Policies - Derivative Financial Instruments (Details) € in Millions, $ in Millions, ¥ in Billions	Jul. 10, 2018 USD ($)	Sep. 30, 2018 USD ($) DerivativeInstrument item	Sep. 30, 2018 EUR (€) DerivativeInstrument item	Jul. 10, 2018 JPY (¥)	Jul. 10, 2018 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2018 EUR (€)	Dec. 31, 2017 USD ($) DerivativeInstrument	Dec. 31, 2017 EUR (€) DerivativeInstrument
Derivative Financial Instruments
Number of credit-risk-related hedging or derivative activities \| item		0	0
Interest rate swap \| Designated as Hedging Instrument
Derivative Financial Instruments
Number of Instruments \| DerivativeInstrument		0	0					0	0
USD-Euro currency forward contract \| May 15, 2019 \| Net Investment Hedging \| Designated as Hedging Instrument
Derivative Financial Instruments
Notional Amount \| €			€ 50.0						€ 50.0
Forward contract net, fair value		$ 0.4						$ (2.4)
USD-Euro currency forward contract \| May 15, 2019 \| Net Investment Hedging \| Designated as Hedging Instrument
Derivative Financial Instruments
Notional Amount \| €			50.0						50.0
Forward contract net, fair value		(2.1)						(4.9)
USD-Euro currency forward contract \| May 15, 2020 \| Net Investment Hedging \| Designated as Hedging Instrument
Derivative Financial Instruments
Notional Amount \| €			50.0						50.0
Forward contract net, fair value		(2.9)						(5.2)
USD-Euro currency forward contract \| May 14, 2021 \| Net Investment Hedging \| Designated as Hedging Instrument
Derivative Financial Instruments
Notional Amount \| €			€ 50.0						€ 50.0
Forward contract net, fair value		(3.6)						(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 \| Deferred costs and other assets \| Net Investment Hedging \| Designated as Hedging Instrument
Derivative Financial Instruments
Fair value of cross currency		4.0
Euro denominated cross currency swap \| Net Investment Hedging \| Designated as Hedging Instrument
Derivative Financial Instruments
Notional Amount \| €							€ 121.6
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		8.0
Simon Property Group, L.P.
Derivative Financial Instruments
Gross accumulated other comprehensive income related to derivative activities		35.6						$ 9.3
Simon Property Group, L.P. \| Credit Facility \| Unsecured Debt
Derivative Financial Instruments
Maximum borrowing capacity		$ 4,000.0
Simon Property Group, L.P. \| Yen \| Credit Facility \| Unsecured Debt
Derivative Financial Instruments
Debt repaid	$ 201.3