Summary of  Significant Accounting Policies - Real Estate (Details)  | 
12 Months Ended | 
|---|---|
Sep. 30, 2018  | |
| Minimum | |
| Real Estate Properties [Line Items] | |
| Percentage of sales price (at least) | 20.00% | 
| Maximum | |
| Real Estate Properties [Line Items] | |
| Percentage of sales price (at least) | 25.00% | 
| X | ||||||||||
- Definition Revenue Recognition, Payments Received as a Percent Of Sales Price. No definition available. 
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
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| X | ||||||||||
- Details 
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- Details 
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