v3.26.1
Significant Accounting Policies - Derivative Financial Instruments (Details)
€ in Millions, $ in Millions
6 Months Ended
Jun. 30, 2026
USD ($)
Y
€ / shares
DerivativeInstrument
Jun. 30, 2025
USD ($)
Jun. 30, 2026
EUR (€)
Y
€ / shares
DerivativeInstrument
Dec. 31, 2025
USD ($)
Y
€ / shares
DerivativeInstrument
Dec. 31, 2025
EUR (€)
Y
€ / shares
DerivativeInstrument
Derivative Financial Instruments          
Number of credit-risk-related hedging or derivative activities | DerivativeInstrument 0   0    
Unamortized gain on treasury locks and terminated hedges $ 31.9     $ 35.3  
Amount expected to be reclassified from accumulated other comprehensive loss to earnings within the next year 6.2        
Gains (losses) of cumulative translation adjustment 53.7 $ (242.6)      
Gross accumulated other comprehensive income (loss) related to derivative activities 52.1     25.0  
Exchange traded option | Option pricing model          
Derivative Financial Instruments          
Forward contract net, fair value 71.1     205.1  
Simon Property Group, L.P          
Derivative Financial Instruments          
Gross accumulated other comprehensive income (loss) related to derivative activities $ 61.1     $ 29.3  
Klepierre | Exchange traded option | Option pricing model | Stock price          
Derivative Financial Instruments          
Derivative liability measurement input | € / shares 36.54   36.54 33.74 33.74
Klepierre | Exchange traded option | Option pricing model | Implied volatility          
Derivative Financial Instruments          
Derivative liability measurement input 0.1962   0.1962 0.1778 0.1778
Klepierre | Exchange traded option | Option pricing model | EUR risk-free rate          
Derivative Financial Instruments          
Derivative liability measurement input 0.0239   0.0239 0.0204 0.0204
Klepierre | Exchange traded option | Option pricing model | Expected dividend yield          
Derivative Financial Instruments          
Derivative liability measurement input 0.0468   0.0468 0.0506 0.0506
Klepierre | Exchange traded option | Option pricing model | Expected term          
Derivative Financial Instruments          
Derivative liability measurement input | Y 0.37   0.37 0.87 0.87
Klepierre | Exchange traded option | Option pricing model | Credit Spread          
Derivative Financial Instruments          
Derivative liability measurement input 0.0015   0.0015 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 $ 3.0     $ 1.5  
Interest rate swap | Location, Statement of Financial Position, Balance [Axis]: us-gaap:OtherLiabilities          
Derivative Financial Instruments          
Interest rate derivative liabilities, fair value $ 10.0     $ 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 | €     € 225.4   € 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 | €     € 94.1   € 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 8, 2026 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €     100.0    
Forward contract net, fair value $ 3.1        
Euro-USD currency forward contract | July 15, 2026 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €     50.0   50.0
Forward contract net, fair value 2.1     0.1  
Euro-USD currency forward contract | July 15, 2026 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €     75.0    
Forward contract net, fair value 1.2        
Euro-USD currency forward contract | July 15, 2026 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €     15.0    
Forward contract net, fair value 0.4        
Euro-USD currency forward contract | August 14,2026 | Net Investment Hedging | Designated as Hedging Instrument          
Derivative Financial Instruments          
Notional Amount | €     100.0    
Forward contract net, fair value 3.2        
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 4.1     $ 0.3  
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 (0.4)        
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 $ (0.4)