Fair Value Measurements (Details 1) (Fair Value, Inputs, Level 3 [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Assets, fair value disclosure
Notes receivable, fair value	$ 43,840	$ 43,957
CMBS	5,370	2,980
Other securities	12,889	10,800
Liabilities, fair value disclosure
Debt fair value	1,805,930	1,674,019
Deferred acquisition fees payable	18,130	30,875
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Assets, fair value disclosure
Notes receivable, fair value	40,000	40,000
CMBS	2,648	2,075
Other securities	8,301	8,301
Liabilities, fair value disclosure
Debt fair value	1,795,336	1,633,452
Deferred acquisition fees payable	$ 17,140	$ 26,246