Real Estate Fund Investments - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Apr. 30, 2016	Dec. 31, 2017
Investment Holdings [Line Items]
Capital commitments	$ 775,200,000
Capital commitments invested		$ 369,950,000
Investment maturity date range start		2018-10
Investment maturity date range end		2027-12
Investment period end date		2019-04
Investment Extended Period End Date		2020-04
Alternative Investment Fund, Interest Rate		1.30%
Minimum
Investment Holdings [Line Items]
Stated interest rates on invested capital commitments		5.50%
Maximum
Investment Holdings [Line Items]
Stated interest rates on invested capital commitments		9.61%