Fair Value Measurements - Schedule of Fair Values of Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	$ 21,398	$ 21,521
Total assets	21,398	437,959
Interest rate swap liabilities	116,943	93,936
Total liabilities	116,943	93,936
Investments in Property Funds		248,824
Investments in Alternative Investment Funds		167,614
Total real estate fund investments		416,438
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	21,398	21,521
Total assets	21,398	21,521
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Interest rate swap liabilities	116,943	93,936
Total liabilities	$ 116,943	93,936
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets		416,438
Investments in Property Funds		248,824
Investments in Alternative Investment Funds		167,614
Total real estate fund investments		$ 416,438