Fair Value Measurements (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) investment	Dec. 31, 2018 USD ($) investment
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Real estate fund investments	$ 222,649	$ 318,758
Real estate fund investments
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Number of investments held by fund | investment	4	4
Real estate fund investments	$ 222,649	$ 318,758
Excess of fair value below cost	112,915
Recurring
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Real estate fund investments	222,649	318,758
Recurring | Level 3
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Real estate fund investments	$ 222,649	$ 318,758
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 | investment	4