v3.26.3
Significant Accounting Policies - Derivative Financial Instruments (Details)
€ in Millions, $ in Millions
9 Months Ended
Sep. 30, 2026
USD ($)
Y
€ / shares
DerivativeInstrument
Sep. 30, 2025
USD ($)
Sep. 30, 2026
EUR (€)
Y
€ / shares
DerivativeInstrument
Dec. 31, 2025
USD ($)
€ / shares
Y
DerivativeInstrument
Dec. 31, 2025
EUR (€)
€ / shares
Y
DerivativeInstrument
Derivative Financial Instruments          
Number of credit-risk-related hedging or derivative activities | DerivativeInstrument 0   0    
Unamortized gain on treasury locks and terminated hedges $ 30.2     $ 35.3  
Amount expected to be reclassified from accumulated other comprehensive loss to earnings within the next year 5.6        
Gains (losses) of cumulative translation adjustment 66.5 $ (239.4)      
Gross accumulated other comprehensive income (loss) related to derivative activities 67.7     25.0  
Exchange traded option | Option pricing model          
Derivative Financial Instruments          
Forward contract net, fair value 9.5     205.1  
Simon Property Group, L.P          
Derivative Financial Instruments          
Gross accumulated other comprehensive income (loss) related to derivative activities $ 79.5     $ 29.3  
Klepierre | Exchange traded option | Option pricing model | Stock price          
Derivative Financial Instruments          
Derivative liability measurement input | € / shares 35.34   35.34 33.74 33.74
Klepierre | Exchange traded option | Option pricing model | Implied volatility          
Derivative Financial Instruments          
Derivative liability measurement input 0.1343   0.1343 0.1778 0.1778
Klepierre | Exchange traded option | Option pricing model | EUR risk-free rate          
Derivative Financial Instruments          
Derivative liability measurement input 0.0268   0.0268 0.0204 0.0204
Klepierre | Exchange traded option | Option pricing model | Expected dividend yield          
Derivative Financial Instruments          
Derivative liability measurement input 0.0483   0.0483 0.0506 0.0506
Klepierre | Exchange traded option | Option pricing model | Expected term          
Derivative Financial Instruments          
Derivative liability measurement input | Y 0.12   0.12 0.87 0.87
Klepierre | Exchange traded option | Option pricing model | Credit Spread          
Derivative Financial Instruments          
Derivative liability measurement input 0.0009   0.0009 0.0045 0.0045
Interest rate swap | Location, Statement of Financial Position, Balance [Axis]: us-gaap:DeferredCostsAndOtherAssets          
Derivative Financial Instruments          
Interest rate derivative assets, fair value $ 10.2     $ 1.5  
Interest rate swap | Location, Statement of Financial Position, Balance [Axis]: us-gaap:OtherLiabilities          
Derivative Financial Instruments          
Interest rate derivative liabilities, fair value $ 55.1     $ 12.8  
US denominated interest rate swap          
Derivative Financial Instruments          
Number of Instruments | DerivativeInstrument 10   10 7 7
Notional Amount $ 2,100.0     $ 2,200.0  
Euro denominated interest rate swap          
Derivative Financial Instruments          
Number of Instruments | DerivativeInstrument 3   3 3 3
Notional Amount | €     € 224.2   € 541.7
US denominated interest rate cap          
Derivative Financial Instruments          
Number of Instruments | DerivativeInstrument 1   1 1 1
Notional Amount $ 85.0     $ 85.0  
Euro denominated interest rate cap          
Derivative Financial Instruments          
Number of Instruments | DerivativeInstrument 1   1 3 3
Notional Amount | €     € 83.1   € 178.8
Euro-USD currency forward contract | January 15 2026 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €         125.0
Forward contract net, fair value       $ 0.3  
Euro-USD currency forward contract | January 15 2026 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €         125.0
Forward contract net, fair value       0.3  
Euro-USD currency forward contract | February 18, 2026 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €         50.5
Forward contract net, fair value       (0.4)  
Euro-USD currency forward contract | March 16 2026 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €         50.0
Forward contract net, fair value       0.1  
Euro-USD currency forward contract | May 15, 2026 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €         50.0
Forward contract net, fair value       0.1  
Euro-USD currency forward contract | July 15, 2026 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €         50.0
Forward contract net, fair value       0.1  
Euro-USD currency forward contract | October 15, 2026 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €     75.0    
Forward contract net, fair value $ 1.0        
Euro-USD currency forward contract | October 15, 2026 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €     50.0    
Forward contract net, fair value 0.6        
Euro-USD currency forward contract | October 15, 2026 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €     15.0    
Forward contract net, fair value 0.2        
Euro-USD currency forward contract | December 14, 2026 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €     100.0    
Forward contract net, fair value 2.4        
Euro-USD currency forward contract | January 15, 2027 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €     100.0   € 100.0
Forward contract net, fair value 5.6     $ 0.3  
Euro-USD currency forward contract | January 15, 2027 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €     100.0    
Forward contract net, fair value 1.3        
Euro-USD currency forward contract | February 16, 2027 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €     80.0    
Forward contract net, fair value 2.1        
Euro-USD currency forward contract | March 15, 2027 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €     79.0    
Forward contract net, fair value 0.8        
Euro-USD currency forward contract | June 14, 2027 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €     € 75.0    
Forward contract net, fair value $ 0.7