Interest and Other Investment Income, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interest and Other Investment Income (Loss), Net
Dividends on marketable securities	$ 13,135	$ 12,836	$ 12,707
Mark-to-market of investments in our deferred compensation plan	5,213	111	11,557
Interest on loans receivable	3,890	6,371	6,107
Other, net	7,308	7,660	8,381
Interest and other investment (loss) income, net	$ 29,546	$ 26,978	$ 38,752