Fair Value (Details) (USD $)										6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014 Recurring basis Level 1	Jun. 30, 2014 Recurring basis Level 2	Dec. 31, 2013 Recurring basis Level 2	Jun. 30, 2014 Recurring basis Level 3	Dec. 31, 2013 Recurring basis Level 3	Jun. 30, 2014 Recurring basis Total	Dec. 31, 2013 Recurring basis Total	Jun. 30, 2014 Minimum	Jun. 30, 2014 Maximum
Financial assets accounted for at fair value on a recurring basis by level within fair value hierarchy
Investments in private equity funds, at fair value	$ 196,810,000	$ 156,616,000	$ 0	$ 0		$ 144,804,000	$ 156,616,000	$ 144,804,000	$ 156,616,000
Real estate securities, available for sale	70,500,000	66,450,000	0	70,500,000	66,450,000			70,500,000	66,450,000
Discount rate (percent)										19.00%	26.00%
Financial assets measured at non-recurring basis	0	0
Financial liabilities measured at non-recurring basis	$ 0	$ 0