Interest and Other Investment Income, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Dividends on marketable securities	$ 3,215	$ 3,200	$ 9,620	$ 9,504
Mark-to-market of investments in our deferred compensation plan	(2,577)	1,352	(327)	8,132
Interest on loans receivable	1,154	1,129	5,113	4,843
Other, net	1,368	1,887	5,212	6,335
Interest and other investment (loss) income, net	$ 3,160	$ 7,568	$ 19,618	$ 28,814