Fair Value Measurements - Fair Value Inputs of Long-Lived Assets Held for Sale (Details) - Fair Value Estimated Using Signed Purchase and Sale Agreement - Retail
Jun. 30, 2019
ft²
$ / ft²
Dec. 31, 2018
ft²
$ / ft²
Measurement Input, Price Per Square Foot    
Long Lived Assets Held-for-sale [Line Items]    
Long-lived assets held for sale, measurement input 73.01 126.73
Measurement Input, Price Per Square Foot | Weighted Average    
Long Lived Assets Held-for-sale [Line Items]    
Long-lived assets held for sale, measurement input 73.01 126.73
Measurement Input, Square Footage    
Long Lived Assets Held-for-sale [Line Items]    
Long-lived assets held for sale, measurement input | ft² 6,840 63,128