Summary of Significant Accounting Policies (Details 6) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011 Item	Dec. 31, 2010
Loans Held for Investment
Number of mortgage and mezzanine loans secured by real estate		3
Aggregate carrying values of mortgages and mezzanine loans		$ 162,832,000
Interest income on loans held for investment	$ 6,800,000	$ 24,300,000	$ 4,600,000

The carrying amount of the outstanding balance due under the mortgage loan.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 948

-SubTopic 310

-Section S99

-Paragraph 1

-Subparagraph (SX 210.12-29)

-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 10

-Section S99

-Paragraph 6

-Subparagraph (SX 210.5-04.(c) Schedule IV)

-URI http://asc.fasb.org/extlink&oid=6882300&loc=d3e5864-122674

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 29

-Article 12

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph c

-Subparagraph Schedule IV

-Article 5

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