Annual report pursuant to Section 13 and 15(d)

Equity and Mezzanine Equity - Additional Information (Detail)

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Equity and Mezzanine Equity - Additional Information (Detail)
 1 Months Ended 12 Months Ended
Oct. 30, 2018
USD ($)
ft²
shares
Apr. 11, 2018
shares
Feb. 29, 2016
USD ($)
Dec. 31, 2018
USD ($)
shares
Dec. 31, 2017
USD ($)
shares
Jun. 30, 2016
USD ($)
Jul. 25, 2014
ft²
Class of Stock [Line Items]              
Authorized but unissued shares reclassified from senior common stock to common stock | shares   3,500,000          
Senior common stock, authorized shares unissued (in shares) | shares   57,969          
Common stock, shares authorized (in shares) | shares   87,700,000   87,700,000 [1] 34,200,000 [1]    
Aggregate Square Footage | ft²             81,371
Aggregate Purchase Price       $ 63,245,000 $ 132,157,000    
Series D Cumulative Redeemable Preferred Stock              
Class of Stock [Line Items]              
Minimum vote need to trigger change in control from tender offer (as percent)       90.00%      
Preferred Stock | Series D Cumulative Redeemable Preferred Stock              
Class of Stock [Line Items]              
Preferred stock, dividend rate (as percent)     7.00%        
Cantor Fitzgerald & Co | Preferred Stock | Series D Cumulative Redeemable Preferred Stock              
Class of Stock [Line Items]              
Maximum aggregate sales price of shares to be issued under open market sale agreement           $ 50,000,000.0  
Remaining capacity to sell preferred stock       $ 18,600,000      
Cantor Fitzgerald & Co | Common Stock ATM Program | Common Stock and Non-controlling OP Units              
Class of Stock [Line Items]              
Maximum aggregate sales price of shares to be issued under open market sale agreement     $ 160,000,000        
Number of shares sold (in shares) | shares       800,000      
Net proceeds from sale of shares       $ 16,100,000      
Open market dale agreement, value of remaining capacity       69,900,000      
Cantor Fitzgerald & Co | Series A and B Preferred Stock ATM Programs | Preferred Stock              
Class of Stock [Line Items]              
Remaining capacity to sell preferred stock       $ 37,200,000      
Cantor Fitzgerald & Co | Series A and B Preferred Stock ATM Programs | Preferred Stock | Series A Cumulative Redeemable Preferred Stock              
Class of Stock [Line Items]              
Preferred stock, dividend rate (as percent)     7.75%        
Cantor Fitzgerald & Co | Series A and B Preferred Stock ATM Programs | Preferred Stock | Series B Cumulative Redeemable Preferred Stock              
Class of Stock [Line Items]              
Maximum aggregate sales price of shares to be issued under open market sale agreement     $ 40,000,000        
Preferred stock, dividend rate (as percent)     7.50%        
Cantor Fitzgerald & Co | Series D Preferred Stock ATM Program | Series D Cumulative Redeemable Preferred Stock              
Class of Stock [Line Items]              
Number of shares sold (in shares) | shares       100,000      
Net proceeds from sale of shares       $ 2,200,000      
Operating Partnership              
Class of Stock [Line Items]              
Company ownership percentage of voting securities       97.50% 100.00%    
Detroit, Michigan              
Class of Stock [Line Items]              
Number of units issued in acquisition (in shares) | shares 742,937            
Aggregate Square Footage | ft² 218,703            
Aggregate Purchase Price $ 21,700,000            
Units held by noncontrolling owners (in shares) | shares         0    
[1] Refer to Note 10 “Equity and Mezzanine Equity”