Fair Value Measurements - Fair Value Inputs of Long-Lived Assets Held and Used (Details)
12 Months Ended
Dec. 31, 2020
ft²
Property
$ / Sqft
Dec. 31, 2019
ft²
Property
$ / Sqft
Fair Value Estimated Using Comparable Properties | Retail    
Impaired Long Lived Assets Held Used And Held For Sale Properties [Line Items]    
Number Of Properties Accounted For At Fair Value | Property 10 4
Fair Value Estimated Using Comparable Properties | Office    
Impaired Long Lived Assets Held Used And Held For Sale Properties [Line Items]    
Number Of Properties Accounted For At Fair Value | Property 1  
Fair Value Estimated Using Comparable Properties | Measurement Input, Price Per Square Foot | Retail | Weighted Average    
Impaired Long Lived Assets Held Used And Held For Sale Properties [Line Items]    
Price per square foot 57.62 104.84
Fair Value Estimated Using Comparable Properties | Measurement Input, Price Per Square Foot | Retail | Minimum    
Impaired Long Lived Assets Held Used And Held For Sale Properties [Line Items]    
Price per square foot 4.35 34.45
Fair Value Estimated Using Comparable Properties | Measurement Input, Price Per Square Foot | Retail | Maximum    
Impaired Long Lived Assets Held Used And Held For Sale Properties [Line Items]    
Price per square foot 282.08 740.74
Fair Value Estimated Using Comparable Properties | Measurement Input, Price Per Square Foot | Office | Weighted Average    
Impaired Long Lived Assets Held Used And Held For Sale Properties [Line Items]    
Price per square foot 89.25  
Fair Value Estimated Using Comparable Properties | Measurement Input, Price Per Square Foot | Office | Minimum    
Impaired Long Lived Assets Held Used And Held For Sale Properties [Line Items]    
Price per square foot 79.80  
Fair Value Estimated Using Comparable Properties | Measurement Input, Price Per Square Foot | Office | Maximum    
Impaired Long Lived Assets Held Used And Held For Sale Properties [Line Items]    
Price per square foot 103.79  
Fair Value Estimated Using Comparable Properties | Measurement Input, Square Footage | Retail    
Impaired Long Lived Assets Held Used And Held For Sale Properties [Line Items]    
Square Footage | ft² 431,563 35,885
Fair Value Estimated Using Comparable Properties | Measurement Input, Square Footage | Office    
Impaired Long Lived Assets Held Used And Held For Sale Properties [Line Items]    
Square Footage | ft² 28,804  
Fair Value Estimated Using Listing Price or Broker Opinion of Value | Retail    
Impaired Long Lived Assets Held Used And Held For Sale Properties [Line Items]    
Number Of Properties Accounted For At Fair Value | Property 11 10
Fair Value Estimated Using Listing Price or Broker Opinion of Value | Office    
Impaired Long Lived Assets Held Used And Held For Sale Properties [Line Items]    
Number Of Properties Accounted For At Fair Value | Property   1
Fair Value Estimated Using Listing Price or Broker Opinion of Value | Measurement Input, Price Per Square Foot | Retail | Weighted Average    
Impaired Long Lived Assets Held Used And Held For Sale Properties [Line Items]    
Price per square foot 43.32 50.71
Fair Value Estimated Using Listing Price or Broker Opinion of Value | Measurement Input, Price Per Square Foot | Retail | Minimum    
Impaired Long Lived Assets Held Used And Held For Sale Properties [Line Items]    
Price per square foot 16.67 24.78
Fair Value Estimated Using Listing Price or Broker Opinion of Value | Measurement Input, Price Per Square Foot | Retail | Maximum    
Impaired Long Lived Assets Held Used And Held For Sale Properties [Line Items]    
Price per square foot 338.98 323.00
Fair Value Estimated Using Listing Price or Broker Opinion of Value | Measurement Input, Price Per Square Foot | Office    
Impaired Long Lived Assets Held Used And Held For Sale Properties [Line Items]    
Price per square foot   99.37
Fair Value Estimated Using Listing Price or Broker Opinion of Value | Measurement Input, Price Per Square Foot | Office | Weighted Average    
Impaired Long Lived Assets Held Used And Held For Sale Properties [Line Items]    
Price per square foot   99.37
Fair Value Estimated Using Listing Price or Broker Opinion of Value | Measurement Input, Square Footage | Retail    
Impaired Long Lived Assets Held Used And Held For Sale Properties [Line Items]    
Square Footage | ft² 577,945 165,773
Fair Value Estimated Using Listing Price or Broker Opinion of Value | Measurement Input, Square Footage | Office    
Impaired Long Lived Assets Held Used And Held For Sale Properties [Line Items]    
Square Footage | ft²   4,310