Fair Value Measurements - Fair Value Inputs of Long-Lived Assets Held and Used (Details)
Jun. 30, 2019
ft²
$ / ft²
Dec. 31, 2018
ft²
$ / ft²
Fair Value Estimated Using Comparable Properties | Measurement Input, Price Per Square Foot | Retail    
Impaired Long-Lived Assets Held and Used [Line Items]    
Long-lived assets held-for-use, measurement input   0
Fair Value Estimated Using Comparable Properties | Measurement Input, Price Per Square Foot | Retail | Minimum    
Impaired Long-Lived Assets Held and Used [Line Items]    
Long-lived assets held-for-use, measurement input 32.85  
Fair Value Estimated Using Comparable Properties | Measurement Input, Price Per Square Foot | Retail | Maximum    
Impaired Long-Lived Assets Held and Used [Line Items]    
Long-lived assets held-for-use, measurement input 740.74  
Fair Value Estimated Using Comparable Properties | Measurement Input, Price Per Square Foot | Retail | Weighted Average    
Impaired Long-Lived Assets Held and Used [Line Items]    
Long-lived assets held-for-use, measurement input 276.84 0
Fair Value Estimated Using Comparable Properties | Measurement Input, Square Footage | Retail    
Impaired Long-Lived Assets Held and Used [Line Items]    
Long-lived assets held-for-use, measurement input | ft² 103,784 0
Fair Value Estimated Using Listing Price or Broker Opinion of Value | Measurement Input, Price Per Square Foot | Retail | Minimum    
Impaired Long-Lived Assets Held and Used [Line Items]    
Long-lived assets held-for-use, measurement input 37.88 185.42
Fair Value Estimated Using Listing Price or Broker Opinion of Value | Measurement Input, Price Per Square Foot | Retail | Maximum    
Impaired Long-Lived Assets Held and Used [Line Items]    
Long-lived assets held-for-use, measurement input 137.25 638.72
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 and Used [Line Items]    
Long-lived assets held-for-use, measurement input 48.95 507.11
Fair Value Estimated Using Listing Price or Broker Opinion of Value | Measurement Input, Price Per Square Foot | Office    
Impaired Long-Lived Assets Held and Used [Line Items]    
Long-lived assets held-for-use, measurement input 0 225.04
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 and Used [Line Items]    
Long-lived assets held-for-use, measurement input 0 225.04
Fair Value Estimated Using Listing Price or Broker Opinion of Value | Measurement Input, Square Footage | Retail    
Impaired Long-Lived Assets Held and Used [Line Items]    
Long-lived assets held-for-use, measurement input | ft² 52,866 27,302
Fair Value Estimated Using Listing Price or Broker Opinion of Value | Measurement Input, Square Footage | Office    
Impaired Long-Lived Assets Held and Used [Line Items]    
Long-lived assets held-for-use, measurement input | ft² 0 5,999