Fair Value Measurements - Fair Value Inputs of Long-Lived Assets Held and Used (Details)
3 Months Ended 12 Months Ended
Mar. 31, 2017
ft²
$ / ft²
Dec. 31, 2016
ft²
$ / ft²
Dec. 31, 2015
$ / ft²
Weighted Average Sale Price Per Square Foot of Comparable Properties [Member] | Retail      
Impaired Long-Lived Assets Held and Used [Line Items]      
Property square footage (per sqft) | ft² 113,943 290,770  
Weighted Average Sale Price Per Square Foot of Comparable Properties [Member] | Retail | Minimum      
Impaired Long-Lived Assets Held and Used [Line Items]      
Sales price (in usd per sqft) 44.19 17.17  
Weighted Average Sale Price Per Square Foot of Comparable Properties [Member] | Retail | Maximum      
Impaired Long-Lived Assets Held and Used [Line Items]      
Sales price (in usd per sqft) 80.11 502.23  
Weighted Average Sale Price Per Square Foot of Comparable Properties [Member] | Retail | Weighted Average      
Impaired Long-Lived Assets Held and Used [Line Items]      
Sales price (in usd per sqft) 56.28 58.78  
Weighted Average Sale Price Per Square Foot of Comparable Properties [Member] | Industrial      
Impaired Long-Lived Assets Held and Used [Line Items]      
Property square footage (per sqft) | ft² 0 104,864  
Weighted Average Sale Price Per Square Foot of Comparable Properties [Member] | Industrial | Weighted Average      
Impaired Long-Lived Assets Held and Used [Line Items]      
Sales price (in usd per sqft) 0.00 26.43  
Weighted Average Sale Price Per Square Foot of Comparable Properties [Member] | Office      
Impaired Long-Lived Assets Held and Used [Line Items]      
Property square footage (per sqft) | ft² 0 135,675  
Weighted Average Sale Price Per Square Foot of Comparable Properties [Member] | Office | Weighted Average      
Impaired Long-Lived Assets Held and Used [Line Items]      
Sales price (in usd per sqft) 0.00 35.00  
Weighted Average Listing Price or Broker Opinion of Value Per Square Foot | Retail      
Impaired Long-Lived Assets Held and Used [Line Items]      
Property square footage (per sqft) | ft² 376,426 516,916  
Weighted Average Listing Price or Broker Opinion of Value Per Square Foot | Retail | Minimum      
Impaired Long-Lived Assets Held and Used [Line Items]      
Listing price and broker opinion (in usd per sqft) 9.13 15.40  
Weighted Average Listing Price or Broker Opinion of Value Per Square Foot | Retail | Maximum      
Impaired Long-Lived Assets Held and Used [Line Items]      
Listing price and broker opinion (in usd per sqft) 139.10   170.02
Weighted Average Listing Price or Broker Opinion of Value Per Square Foot | Retail | Weighted Average      
Impaired Long-Lived Assets Held and Used [Line Items]      
Listing price and broker opinion (in usd per sqft) 35.02 40.80  
Weighted Average Listing Price or Broker Opinion of Value Per Square Foot | Industrial      
Impaired Long-Lived Assets Held and Used [Line Items]      
Property square footage (per sqft) | ft² 588,906 149,627  
Weighted Average Listing Price or Broker Opinion of Value Per Square Foot | Industrial | Minimum      
Impaired Long-Lived Assets Held and Used [Line Items]      
Listing price and broker opinion (in usd per sqft) 4.01    
Weighted Average Listing Price or Broker Opinion of Value Per Square Foot | Industrial | Maximum      
Impaired Long-Lived Assets Held and Used [Line Items]      
Listing price and broker opinion (in usd per sqft) 14.61    
Weighted Average Listing Price or Broker Opinion of Value Per Square Foot | Industrial | Weighted Average      
Impaired Long-Lived Assets Held and Used [Line Items]      
Listing price and broker opinion (in usd per sqft) 6.33 9.09  
Weighted Average Listing Price or Broker Opinion of Value Per Square Foot | Office      
Impaired Long-Lived Assets Held and Used [Line Items]      
Property square footage (per sqft) | ft² 141,525 34,992  
Weighted Average Listing Price or Broker Opinion of Value Per Square Foot | Office | Weighted Average      
Impaired Long-Lived Assets Held and Used [Line Items]      
Listing price and broker opinion (in usd per sqft) 62.89 56.81