Real Estate Debt Investments (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 investment	Mar. 31, 2012 investment	Dec. 31, 2012
Maturities of principal amounts of CRE debt investments
Total	$ 649,613		$ 543,619
Credit Quality Monitoring
Number of CRE debt investments contributing to more than 10% of interest income	2	4
Minimum
Credit Quality Monitoring
Period past due on contractual debt service payments for debt investments to be categorized as non-performing loans	90 days
Initial Maturity
Maturities of principal amounts of CRE debt investments
April 1 - December 31, 2013	64,480
2014	115,763
2015	313,570
2016	155,800
Total	649,613
Maturity Including Extensions
Maturities of principal amounts of CRE debt investments
2014	52,000
2015	12,480
2016	75,013
2017	354,320
Thereafter	155,800
Total	$ 649,613