Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity (Details)

v3.8.0.1
Stockholders' Equity (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 1 Months Ended 3 Months Ended 12 Months Ended
Jul. 11, 2016
Jul. 02, 2016
Mar. 02, 2016
Sep. 15, 2017
Jun. 30, 2017
Jul. 31, 2016
Dec. 31, 2017
Nov. 30, 2017
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Preferred Stock, Shares Authorized             10,000   10,000 10,000  
Preferred Stock, Par or Stated Value Per Share             $ 0.001   $ 0.001 $ 0.001  
Preferred Stock, Shares Issued             3,105   3,105 0  
Preferred Stock, Shares Outstanding             3,105   3,105 0  
Common Stock, Shares Authorized             500,000   500,000 500,000  
Common Stock, Par or Stated Value Per Share             $ 0.001   $ 0.001 $ 0.001  
Common Stock, Shares, Outstanding             21,631   21,631 17,606  
Stock Issued During Period, Value, New Issues                   $ 138,969  
Beneficial Ownership Description                 The Companys charter provides that, subject to certain exceptions, no person may beneficially or constructively own more than 9.8%, in value or in number of shares, whichever is more restrictive, of the outstanding shares of any class or series of the Companys capital stock. On June27, 2016, the Board approved a waiver of the 9.8% ownership limit in the Companys charter allowing ZH USA, LLC to own up to 16.9% of the Companys outstanding shares of common stock.    
Dividends Payable             $ 5,638   $ 5,638 3,604  
Proceeds from Issuance of Common Stock                 $ 33,795 137,288 $ 0
Preferred Stock, Liquidation Preference Per Share             $ 25   $ 25    
Payments of Ordinary Dividends, Preferred Stock and Preference Stock [1]                 $ 745    
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs         $ 443         1,681  
Preferred Stock, Value, Issued             $ 74,959   74,959 0  
Dividends, Preferred Stock             $ 1,455 $ 1,455 1,714    
Payments of dividens, Common Stock, OP and LTIP Units                 (15,231) (3,878) (256)
Reclassification Of Common Stock Offering Cost To Additional Paid In Capital Non Cash Or Partial Non Cash Transaction $ 1,681               443 $ 1,681 $ 0
Common Stock [Member]                      
Stock Issued During Period, Shares, New Issues 15,000       4,025         15,000  
Stock Issued During Period, Value, New Issues         $ 36,225         $ 15  
Shares Issued, Price Per Share         $ 9            
Proceeds from Issuance of Common Stock $ 137,288       $ 33,795            
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs                   $ 0  
Dividends, Preferred Stock                 $ 0    
Measurement Date [Member]                      
Units of Partnership Interest, Amount             11,300   11,300    
Contractual Installment Date [Member]                      
Units of Partnership Interest, Amount             232   232    
Series A Preferred Stock [Member]                      
Preferred Stock, Par or Stated Value Per Share       $ 0.001              
Stock Issued During Period, Shares, New Issues       3,105              
Stock Issued During Period, Value, New Issues       $ 77,625              
Payments of Stock Issuance Costs       $ 221              
Dividends Payable, Amount Per Share             $ 1.875   $ 1.875    
Preferred Stock, Liquidation Preference Per Share       $ 25              
Preferred Stock, Redemption Price Per Share       $ 25              
Preferred Stock, Dividend Rate, Percentage                 7.50%    
Operating Partnership Units [Member]                      
Units of Partnership Interest, Amount             11,532   11,532    
Stock Issued During Period, Shares, Acquisitions                 1,221    
Operating Partnership Units [Member] | Measurement Date [Member]                      
Limited Partners' Capital Account, Units Issued             1,246   1,246    
Long Tem Incentives Plan Units [Member]                      
Dividends Payable             $ 117   $ 117    
IPO [Member] | Common Stock [Member]                      
Stock Issued During Period, Shares, New Issues   13,043                  
Stock Issued During Period, Value, New Issues   $ 130,435                  
Shares Issued, Price Per Share   $ 10.00                  
Proceeds from Issuance Initial Public Offering $ 138,969 $ 120,774                  
Over-Allotment Option [Member] | Common Stock [Member]                      
Stock Issued During Period, Shares, New Issues 1,957                    
Stock Issued During Period, Value, New Issues $ 19,565                    
Shares Issued, Price Per Share $ 10.00                    
Proceeds from Issuance of Common Stock $ 18,195                    
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs         $ 1,987            
Over-Allotment Option [Member] | Series A Preferred Stock [Member]                      
Stock Issued During Period, Shares, New Issues       405              
Payments of Stock Issuance Costs       $ 2,445              
ZH USA, LLC [Member]                      
Debt Conversion, Original Debt, Amount     $ 15,000     $ 15,030          
Debt Conversion, Converted Instrument, Shares Issued     1,177     1,179          
Debt Instrument Convertible, Base for Conversion     $ 12.748     $ 12.748       $ 12.748  
ZH USA, LLC [Member] | Common Stock [Member]                      
Debt Conversion, Original Debt, Amount   $ 15,030 $ 15,000                
Debt Conversion, Converted Instrument, Shares Issued   1,179 1,177                
Debt Instrument Convertible, Base for Conversion   $ 12.748 $ 12.748                
[1] Represents the November 2017 and December 2017 portion of the total $1,455 three month dividend amount.