Fair Value Measurements - Carrying Value and Fair Value Measurements (Details) - Level 3 - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Carrying Value
Fair Value, Balance Sheet Grouping
Mortgage debt, net	$ 1,853,541	$ 1,849,459
Loans receivable	102,359	110,500
CMBS	1,144	6,548
Fair Value
Fair Value, Balance Sheet Grouping
Mortgage debt, net	1,856,737	1,864,043
Loans receivable	110,500	110,500
CMBS	$ 1,144	$ 7,237

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13476-108611

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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.

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- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

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- Definition

Fair value of securitized, pay-through debt securities collateralized by real estate mortgage loans classified as held-to-maturity.

+ References

No definition available.

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