Related Party Transactions and Investments in Non-Consolidated Entities - Management fees and interest income from loans (Details) - USD ($)	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018
Schedule of Equity Method Investments [Line Items]
Asset management fees, low end of range (as a percent)	1.00%
Asset management fees, high end of range (as a percent)	5.00%
Notice period for cancellation of applicable contracts	30 days
Revenue	$ 118,000	$ 271,000
Revenue, Product and Service [Extensible List]	us-gaap:AssetManagement1Member	us-gaap:AssetManagement1Member
Sponsored REITs
Schedule of Equity Method Investments [Line Items]
Impairment of Sponsored REIT	$ 0

High end of the range of the asset management fee as a percentage of collected rents.

No definition available.

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- Definition

Low end of the range of the asset management fee as a percentage of collected rents.

+ References

No definition available.

+ Details

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- Definition

Represents the notice period for cancellation of applicable contracts.

+ References

No definition available.

+ Details

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- Definition

Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953550-111524

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- Definition

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

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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.

+ References

No definition available.

+ Details

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- Definition

Indicates type of revenue from product and service. Includes, but is not limited to, revenue from contract with customer and other sources.

+ References

No definition available.

+ Details

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