Fair Value Measurements - Schedule of Fair Values of Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments in Property Funds	$ 248,824	$ 183,216
Investments in Alternative Investment Funds	167,614	140,171
Total real estate fund investments	416,438	323,387
Marketable securities	21,521	20,159
Total assets	437,959	343,546
Interest rate swap liabilities	93,936	194,196
Total liabilities	93,936	194,196
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	21,521	20,159
Total assets	21,521	20,159
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Interest rate swap liabilities	93,936	194,196
Total liabilities	93,936	194,196
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments in Property Funds	248,824	183,216
Investments in Alternative Investment Funds	167,614	140,171
Total real estate fund investments	416,438	323,387
Total assets	$ 416,438	$ 323,387