Interest and Other Investment Income (Loss), Net (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Total Interest and Other Investment Income, Net	$ 15,681	$ 117,108
Marketable Equity Securities Derivative Positions [Member]
Total Interest and Other Investment Income, Net	1,045	17,163
Mezzanine Loans Loss Accrual [Member]
Total Interest and Other Investment Income, Net	0	82,744
Marketable Securities [Member]
Total Interest and Other Investment Income, Net	6,247	7,667
Mark to Market of deferred Compensation Plan [Member]
Total Interest and Other Investment Income, Net	4,127	4,952
Mezzanine Loans Receivable [Member]
Total Interest and Other Investment Income, Net	2,851	2,644
Other Investment Income [Member]
Total Interest and Other Investment Income, Net	$ 1,411	$ 1,938