Real Estate Fund Investments - Additional Information (Details)	Oct. 29, 2015 USD ($) ft²	Dec. 31, 2015 USD ($) ft²
Investment Holdings [Line Items]
Area of office properties | ft²		10,400,000
Aggregate committed capital		$ 580,200,000
Committed capital invested		$ 166,560,000
Fund VII and VII-H [Member] | 670 Broadway [Member]
Investment Holdings [Line Items]
Area of office properties | ft²	75,945
Business acquisition, consideration amount	$ 112,000,000
Business acquisition, consideration cash	42,000,000
Mortgage Debt [Member] | Fund VII and VII-H [Member] | 670 Broadway [Member]
Investment Holdings [Line Items]
Business acquisition, consideration debt	$ 70,000,000