Fair Value Measurements - Fair Value Inputs of Long-Lived Assets Held and Used (Details) - Fair Value Estimated Using Listing Price or Broker Opinion of Value
Mar. 31, 2019
ft²
$ / ft²
Dec. 31, 2018
ft²
$ / ft²
Measurement Input, Price Per Square Foot | Retail    
Impaired Long-Lived Assets Held and Used [Line Items]    
Long-lived assets held-for-use, measurement input 137.25  
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 137.25 507.11
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   185.42
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   638.72
Measurement Input, Price Per Square Foot | Office    
Impaired Long-Lived Assets Held and Used [Line Items]    
Long-lived assets held-for-use, measurement input 0.00 225.04
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 0.00 225.04
Measurement Input, Square Footage | Retail    
Impaired Long-Lived Assets Held and Used [Line Items]    
Long-lived assets held-for-use, measurement input | ft² 2,788 27,302
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