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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Real estate fund investments
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	$ 455,692	$ 524,150	$ 462,132	$ 574,761
Dispositions/distributions	(91,606)	0	(91,606)	(71,888)
Net unrealized (loss) gain on held investments	(11,220)	(4,764)	(28,860)	16,091
Net realized gains on exited investments	35,620	0	35,861	14,676
Previously recorded unrealized gains on exited investment	(36,736)	0	(25,538)	(14,254)
Other, net	0	0	(239)	0
Ending balance	351,750	519,386	351,750	519,386
Deferred Compensation Plan Assets
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	49,849	60,140	57,444	59,186
Purchases	2,176	1,251	3,989	3,523
Dispositions/distributions	(3,810)	(3,737)	(15,922)	(5,888)
Realized and unrealized gains (losses)	246	(1,055)	2,151	(743)
Other, net	823	316	1,622	837
Ending balance	$ 49,284	$ 56,915	$ 49,284	$ 56,915