Real Estate Fund Investments - Summary of Ownership Interest in Property Funds and Property Funds Ownership Interest in Underlying Properties (Parenthetical) (Details)			12 Months Ended
	Dec. 13, 2017	Jul. 17, 2017	Dec. 31, 2017
One Market Plaza [Member]
Investment Holdings [Line Items]
Ownership interest rate of property			49.00%
One Market Plaza [Member] | Other Investors [Member] | Fund III [Member]
Investment Holdings [Line Items]
Ownership percentage sold	2.00%
50 Beale Street [Member] | Fund VII and Fund VII H [Member]
Investment Holdings [Line Items]
Percentage of ownership interest in new joint venture		36.60%
Ownership percentage sold		42.80%