Loans Receivable and Other Lending Investments, net (Credit Characteristics by Payment Status) (Details) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2017 USD ($) loan	Dec. 31, 2016 USD ($) loan
Recorded investment in loans, aged by payment status and presented by class
Current	$ 871,953	$ 1,229,180
Less Than and Equal to 90 Days	0	0
Greater Than 90 Days	232,155	233,823
Total Past Due	232,155	233,823
Loans	$ 1,104,108	$ 1,463,003
Financing receivable, number of loans greater than 90 days past due \| loan	4	4
Financing receivables, past due time period	90 days	90 days
Minimum
Recorded investment in loans, aged by payment status and presented by class
Financing receivables, past due time period	1 year	1 year
Maximum
Recorded investment in loans, aged by payment status and presented by class
Financing receivables, past due time period	8 years	8 years
Senior mortgages
Recorded investment in loans, aged by payment status and presented by class
Current	$ 521,610	$ 868,505
Less Than and Equal to 90 Days	0	0
Greater Than 90 Days	75,732	76,677
Total Past Due	75,732	76,677
Loans	597,342	945,182
Corporate/Partnership loans
Recorded investment in loans, aged by payment status and presented by class
Current	340,980	335,677
Less Than and Equal to 90 Days	0	0
Greater Than 90 Days	156,423	157,146
Total Past Due	156,423	157,146
Loans	497,403	492,823
Subordinate mortgages
Recorded investment in loans, aged by payment status and presented by class
Current	9,363	24,998
Less Than and Equal to 90 Days	0	0
Greater Than 90 Days	0	0
Total Past Due	0	0
Loans	$ 9,363	$ 24,998

Financing Receivable, Number of Loans Greater than 90 Days Past Due

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- Definition

Financing receivables that are equal to or less than 90 days past due.

+ References

No definition available.

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- Definition

Financing receivables that are greater than 90 days past due.

+ References

No definition available.

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- Definition

Financing Receivables, Past Due Time Period

+ References

No definition available.

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- Definition

Financing receivables that are current.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953401-111524

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- Definition

Recorded Investment in financing receivables that are past due at the balance sheet date.

+ References

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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

Amount representing an agreement for an unconditional promise by the maker to pay the entity (holder) a definite sum of money at a future date. Such amount may include accrued interest receivable in accordance with the terms of the note. The note also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. Excludes amounts related to receivables held-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.10(3))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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