Marketable Securities and Derivative Instruments: Marketable Securities (Details 1) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Equity Securities	$ 382,987	$ 398,188
Available-for-sale Equity Securities, Amortized Cost Basis	214,766	378,757
Available-for-sale Securities, Gross Unrealized Gain (Loss)	168,221	19,431
Lexington Realty Trust [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Equity Securities	217,934	0
Available-for-sale Equity Securities, Amortized Cost Basis	72,549	0
Available-for-sale Securities, Gross Unrealized Gain (Loss)	145,385	0
JC Penney [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Equity Securities	129,704	366,291
Available-for-sale Equity Securities, Amortized Cost Basis	129,704	366,291
Available-for-sale Securities, Gross Unrealized Gain (Loss)	0	0
Other Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Equity Securities	35,349	31,897
Available-for-sale Equity Securities, Amortized Cost Basis	12,513	12,466
Available-for-sale Securities, Gross Unrealized Gain (Loss)	$ 22,836	$ 19,431

Amount of equity securities categorized neither as held-to-maturity nor as trading.

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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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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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Reference 9: 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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

Reference 10: 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.

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