Interest and Other Investment Income (Loss), Net (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total Interest and Other Investment Income, net	$ 26,416	$ (49,172)	$ (22,658)	$ (33,507)
Marketable Equity Securities Derivative Positions [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total Interest and Other Investment Income, net	9,065	(58,732)	(13,475)	(57,687)
Income From Prepayment Penalties [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total Interest and Other Investment Income, net	5,267	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	4,940	3,165	10,017	6,015
Marketable Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Total Interest and Other Investment Income, net	2,770	4,846	5,540	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	2,492	24	5,938	4,151
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	$ 1,882	$ 1,525	$ 3,542	$ 2,921