Fair Value Measurements (Narratives) (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) Investments	Dec. 31, 2015 USD ($) Investments
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Number Of Investments Held By Fund | Investments	6	6
Real estate fund investments	$ 462,132,000	$ 574,761,000
Real estate fund investments
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Real estate fund investments	462,132,000	574,761,000
Excess of fair value over cost	153,197,000
Recurring
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Real estate fund investments	462,132,000	574,761,000
Recurring | Level 3
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Real estate fund investments	$ 462,132,000	$ 574,761,000
Recurring | Level 3 | 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	$ 462,132,000
Excess of fair value over cost	$ 153,197,000
Recurring | Level 3 | Real estate fund investments | Minimum | Discounted Cash Flow Valuation Technique
Fair Value Inputs [Abstract]
Anticipated holding period of investments	1 year
Recurring | Level 3 | Real estate fund investments | Maximum | Discounted Cash Flow Valuation Technique
Fair Value Inputs [Abstract]
Anticipated holding period of investments	4 years