Fair Value Measurements (Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable securities	$ 33,313	$ 152,198	$ 182,752
Real estate fund investments	222,649	318,758
Recurring
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable securities	33,313	152,198
Real estate fund investments	222,649	318,758
Deferred compensation plan assets	103,773	96,524
Interest rate swaps (included in other assets)	4,327	27,033
Total assets	364,062	594,513
Mandatorily redeemable instruments (included in other liabilities)	50,561	50,561
Interest rate swaps (included in other liabilities)	40,354	15,236
Total liabilities	90,915	65,797
Recurring | Level 1
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Marketable securities	33,313	152,198
Real estate fund investments	0	0
Deferred compensation plan assets	71,338	58,716
Interest rate swaps (included in other assets)	0	0
Total assets	104,651	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	0	0
Interest rate swaps (included in other assets)	4,327	27,033
Total assets	4,327	27,033
Mandatorily redeemable instruments (included in other liabilities)	0	0
Interest rate swaps (included in other liabilities)	40,354	15,236
Total liabilities	40,354	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	222,649	318,758
Deferred compensation plan assets	32,435	37,808
Interest rate swaps (included in other assets)	0	0
Total assets	255,084	356,566
Mandatorily redeemable instruments (included in other liabilities)	0	0
Interest rate swaps (included in other liabilities)	0	0
Total liabilities	0	0
Other Assets | Recurring
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Deferred compensation plan assets	91,954	88,122
Restricted Cash | Recurring
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis
Deferred compensation plan assets	$ 11,819	$ 8,402