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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”

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