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Summary of Significant Accounting Policies - Narrative (Details) | Sep. 30, 2019 USD ($) | Jan. 01, 2019 lease_option | Dec. 31, 2018 USD ($)
--- | --- | --- | ---
Significant Accounting Policies [Line Items] |  |  |
Accounts receivable, net representing rental income accrued | $ 42,700,000 |  | $ 43,300,000
Right-of-use asset | 1,800,000 |  |
Operating lease liability | 1,800,000 |  |
Minimum |  |  |
Significant Accounting Policies [Line Items] |  |  |
Allowance for doubtful accounts receivables representing rental income accrued | $ 48,400 |  | $ 58,500
Operating lease term of contract |  | 1 year |
Maximum |  |  |
Significant Accounting Policies [Line Items] |  |  |
Operating lease term of contract |  | 15 years |
Corporate Headquarters |  |  |
Significant Accounting Policies [Line Items] |  |  |
Number of options to extend lease | lease_option |  | 1 |
Lease renewal term |  | 5 years |

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- Definition Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980 + Details
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