Marketable Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Equity Securities	$ 194,489	$ 150,997
Available-for-sale Equity Securities, Amortized Cost Basis	76,928	72,549
Available-for-sale Securities, Gross Unrealized Gain	117,561	78,448
Lexington Realty Trust [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Equity Securities	186,721	147,752
Available-for-sale Equity Securities, Amortized Cost Basis	72,549	72,549
Available-for-sale Securities, Gross Unrealized Gain	114,172	75,203
Other Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Equity Securities	7,768	3,245
Available-for-sale Equity Securities, Amortized Cost Basis	4,379	0
Available-for-sale Securities, Gross Unrealized Gain	$ 3,389	$ 3,245