Fair Value Measurements (Narratives) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) Investments	Dec. 31, 2016 USD ($)
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Real estate fund investments	$ 454,946	$ 462,132
Real estate fund investments
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Number Of Investments Held By Fund | Investments	6
Real estate fund investments	$ 454,946
Excess of fair value over cost	142,346
Recurring
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Real estate fund investments	454,946	462,132
Recurring | Level 3
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Real estate fund investments	454,946	$ 462,132
Excess of fair value over cost	$ 142,346
Recurring | Level 3 | Real estate fund investments | Minimum
Fair Value Inputs [Abstract]
Anticipated holding period of investments	10 months
Recurring | Level 3 | Real estate fund investments | Maximum
Fair Value Inputs [Abstract]
Anticipated holding period of investments	3 years 10 months