Marketable Securities and Derivative Instruments: Marketable Securities (Details 1) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities - available for sale	$ 402,935	$ 398,188
Available-for-sale Equity Securities, Amortized Cost Basis	214,365	378,756
Available-for-sale Securities, Gross Unrealized Gain (Loss)	188,570	19,432
Lexington Realty Trust [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities - available for sale	215,718	0
Available-for-sale Equity Securities, Amortized Cost Basis	72,549	0
Available-for-sale Securities, Gross Unrealized Gain (Loss)	143,169	0
JC Penney [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities - available for sale	146,615	366,291
Available-for-sale Equity Securities, Amortized Cost Basis	129,704	366,291
Available-for-sale Securities, Gross Unrealized Gain (Loss)	16,911	0
Other Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities - available for sale	40,602	31,897
Available-for-sale Equity Securities, Amortized Cost Basis	12,112	12,465
Available-for-sale Securities, Gross Unrealized Gain (Loss)	$ 28,490	$ 19,432

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

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+ Details