Fair Value Measurements (Narratives) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($) Investments	Dec. 31, 2014 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate fund investments	$ 555,414	$ 513,973
Real Estate Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number Of Investments Held By Fund | Investments	6
Real estate fund investments	$ 555,414
Excess of fair value over cost	$ 190,620
Real Estate Fund [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Anticipated Investment Holding Period	9 months 18 days
Real Estate Fund [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Measurement Anticipated Investment Holding Period	5 years 3 months 18 days