Fair Value Measurements (Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable securities	$ 35,751	$ 152,198
Real estate fund investments	306,596	318,758
Recurring
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable securities	35,751	152,198
Real estate fund investments	306,596	318,758
Deferred compensation plan assets (included in restricted cash and other assets)	99,678	96,524
Interest rate swaps (included in other assets)	5,901	27,033
Total assets	447,926	594,513
Mandatorily redeemable instruments (included in other liabilities)	50,561	50,561
Interest rate swaps (included in other liabilities)	49,539	15,236
Total liabilities	100,100	65,797
Recurring | Level 1
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable securities	35,751	152,198
Real estate fund investments	0	0
Deferred compensation plan assets (included in restricted cash and other assets)	72,501	58,716
Interest rate swaps (included in other assets)	0	0
Total assets	108,252	210,914
Mandatorily redeemable instruments (included in other liabilities)	50,561	50,561
Interest rate swaps (included in other liabilities)	0	0
Total liabilities	50,561	50,561
Recurring | Level 2
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable securities	0	0
Real estate fund investments	0	0
Deferred compensation plan assets (included in restricted cash and other assets)	0	0
Interest rate swaps (included in other assets)	5,901	27,033
Total assets	5,901	27,033
Mandatorily redeemable instruments (included in other liabilities)	0	0
Interest rate swaps (included in other liabilities)	49,539	15,236
Total liabilities	49,539	15,236
Recurring | Level 3
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable securities	0	0
Real estate fund investments	306,596	318,758
Deferred compensation plan assets (included in restricted cash and other assets)	27,177	37,808
Interest rate swaps (included in other assets)	0	0
Total assets	333,773	356,566
Mandatorily redeemable instruments (included in other liabilities)	0	0
Interest rate swaps (included in other liabilities)	0	0
Total liabilities	0	0
Restricted Cash | Recurring
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Deferred compensation plan assets (included in restricted cash and other assets)	18,079	8,402
Other Assets | Recurring
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Deferred compensation plan assets (included in restricted cash and other assets)	$ 81,599	$ 88,122