Acquisitions - Additional Information (Details)	Jul. 17, 2017 USD ($)	Sep. 30, 2017 ft²	Jul. 16, 2017 ft² Fund
Business Acquisition [Line Items]
Area of office and retail properties | ft²		12,500,000
Percentage of ownership interest in new joint venture	36.60%
50 Beale Street [Member]
Business Acquisition [Line Items]
Property funds, ownership percentage	31.10%
Number of real estate funds | Fund			2
Percentage of interest directly acquired in property	13.20%
Percentage of ownership interest in new joint venture	36.60%
Percentage of remaining interest acquired in property by new joint venture	49.00%
Value of property acquired | $	$ 517,500,000
Value of debt assumed with acquisition | $	$ 228,000,000
Debt, fixed interest rate	3.65%
Maturity date of debt	2021-10
50 Beale Street [Member] | Fund VII and Fund VII H [Member]
Business Acquisition [Line Items]
Property funds, ownership percentage			3.10%
Property ownership, percentage	42.80%		42.80%
Area of office and retail properties | ft²			660,625
Percentage of interest acquired	62.20%
Percentage of ownership interest in new joint venture	36.60%
50 Beale Street [Member] | Third Party Investors [Member]
Business Acquisition [Line Items]
Property funds, remaining ownership percentage			57.20%