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Risk Management and Derivatives (Risk Concentration) (Details)	12 Months Ended
	Dec. 31, 2017 borrower
Land
Concentration Risk [Line Items]
Concentration risk, percentage	22.10%
Office/Industrial
Concentration Risk [Line Items]
Concentration risk, percentage	20.10%
Commercial Entertainment and Leisure Real Estate
Concentration Risk [Line Items]
Concentration risk, percentage	11.50%
Condominium Units
Concentration Risk [Line Items]
Concentration risk, percentage	11.10%
Mixed Use Collateral
Concentration Risk [Line Items]
Concentration risk, percentage	11.90%
Customer Concentration Risk
Concentration Risk [Line Items]
Number of large borrowers or tenants	5
Concentration risk percentage of revenue (no more than)	15.00%
Concentration risk percentage of one single customer, revenue (no more than)	5.70%
New York | Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage	21.70%
California | Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration risk, percentage	12.10%

X

- Definition

Represents the number of large borrowers considered for evaluating concentration risk.

+ References

No definition available.

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- Definition

Concentration Risk Percentage of Revenue Accounted by Large Borrowers or Tenants

+ References

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- Definition

Concentration Risk, Percentage of Revenue Accounted by One Single Borrower or Tenant

+ 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.

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6351-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13531-108611

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6404-108592

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13537-108611

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