Fair Value Measurements (Details Textual) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Impairment charges	$ 698,000		$ 2,720,000
Fair Value Measurements (Textual) [Abstract]
Net unrealized gains	7,363,000	5,526,000	10,071,000
Transfers between Level 1 and Level 2 fair value assets	0
Transfers between Level 1 and Level 2 fair value liabilities	0
Loan securities carried at fair value	11,000	5,309,000
Loan security face value	1.00%
Atlanta Georgia [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Impairment charges	1,738,000
Denton Texas [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Impairment charges	824,000
Investments in real estate [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Impairment charges	3,260,000	7,600,000
Equity investments [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Trust recognized other-than-temporary impairment losses	0	21,058,000	0
Impairment charges	$ 0	$ 0	$ 0

The charge against earnings resulting from the aggregate write down of all assets from their carrying value to their fair value.

+ References+ Details

The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

+ References

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

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

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

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-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph 16

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

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-Name FASB Staff Position (FSP)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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Reference 7: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details