Interest and Other Investment Income (Loss), Net (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total Interest and Other Investment Income, net	$ (10,275)	$ 10,523	$ (32,933)	$ (22,984)
Marketable Equity Securities Derivative Positions [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total Interest and Other Investment Income, net	(20,012)	4,344	(33,487)	(53,343)
Income From Prepayment Penalties [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total Interest and Other Investment Income, net	0	0	5,267	0
Mezzanine Loans Receivable [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total Interest and Other Investment Income, net	4,766	2,852	14,783	8,867
Marketable Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total Interest and Other Investment Income, net	2,804	0	8,344	11,093
Mark to Market of deferred Compensation Plan [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total Interest and Other Investment Income, net	269	1,116	6,207	5,267
Impairment Losses On Marketable Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total Interest and Other Investment Income, net	0	0	(39,487)	0
Other Investment Income [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total Interest and Other Investment Income, net	$ 1,898	$ 2,211	$ 5,440	$ 5,132