Fair Value Measurements (Changes in the Fair Value of Real Estate Fund Investments and Deferred Compensation Plan Assets) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Real estate fund investments
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	$ 306,596	$ 373,039	$ 318,758	$ 354,804
Purchases/additional fundings	0	0	4,000	68,950
Net unrealized loss on held investments	0	(3,283)	(16,162)	(32,796)
Dispositions	0	0	0	(20,291)
Net realized loss on exited investments	0	0	0	(913)
Other, net	0	11	0	13
Ending balance	306,596	369,767	306,596	369,767
Deferred Compensation Plan Assets
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	21,991	39,870	37,808	40,128
Sales	(652)	(3,304)	(20,807)	(6,813)
Purchases/additional fundings	5,437	1,576	8,314	3,209
Realized and unrealized gains	116	180	854	892
Other, net	285	466	1,008	1,372
Ending balance	$ 27,177	$ 38,788	$ 27,177	$ 38,788