Summary of Significant Accounting Policies - (Details)  | 
 Sep. 30, 2017  
lease 
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|---|---|
| Accounting Policies [Abstract] | |
| Number of operating ground lease arrangements | 2 | 
| X | ||||||||||
- References No definition available. 
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| X | ||||||||||
- Definition The number of units (items of property) under operating lease arrangements. No definition available. 
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