Real Estate Debt Investments (Details) (USD $)	6 Months Ended	12 Months Ended						6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended			6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended		6 Months Ended	12 Months Ended	1 Months Ended	7 Months Ended
	Jun. 30, 2014 loan	Dec. 31, 2013 loan	Jun. 30, 2014 Term Loan Facilities	Dec. 31, 2013 Term Loan Facilities	Dec. 31, 2013 Securitization 2013-1	Jun. 30, 2014 Securitization Bonds Payable	Dec. 31, 2013 Securitization Bonds Payable	Jun. 30, 2014 Weighted Average	Dec. 31, 2013 Weighted Average	Jun. 30, 2014 First mortgage loans loan	Dec. 31, 2013 First mortgage loans loan	Jun. 30, 2014 First mortgage loans Weighted Average	Dec. 31, 2013 First mortgage loans Weighted Average	Jun. 30, 2014 Mezzanine loans loan	Dec. 31, 2013 Mezzanine loans loan	Jun. 30, 2014 Mezzanine loans Weighted Average	Dec. 31, 2013 Mezzanine loans Weighted Average	Jun. 30, 2014 First mortgage loans, mezzanine loans and subordinate mortgage interests	Dec. 31, 2013 First mortgage loans, mezzanine loans and subordinate mortgage interests	Jun. 30, 2014 Subordinate interests loan	Dec. 31, 2013 Subordinate interests loan	Jun. 30, 2014 Subordinate interests Weighted Average	Dec. 31, 2013 Subordinate interests Weighted Average	Dec. 31, 2013 Mortgage Loans on Real Estate, LIBOR	Jun. 30, 2014 Mortgage Loans on Real Estate, LIBOR Weighted Average	Dec. 31, 2013 Mortgage Loans on Real Estate, LIBOR Collateralized Debt Obligations Weighted Average Variable Interest Entity, Primary Beneficiary	Aug. 12, 2014 Subsequent event loan	Aug. 12, 2014 Subsequent event loan	Aug. 11, 2014 Subsequent event	Aug. 11, 2014 Subsequent event First mortgage loans, mezzanine loans and subordinate mortgage interests
CRE debt investments
Number (loans)	34	34								28	29			5	4					1	1						3	7
Principal Amount	$ 1,316,918,000	$ 1,135,323,000								$ 1,102,475,000	$ 915,380,000			$ 181,193,000	$ 186,693,000					$ 33,250,000	$ 33,250,000								$ 406,400,000
Mortgage Loans on Real Estate, Commercial and Consumer, Net, Including Held for Sale		1,092,273,000
Real estate debt investments, net	1,259,805,000	1,074,773,000								1,078,223,000	904,918,000			148,332,000	154,105,000					33,250,000	33,250,000
Allocation by Investment Type (percent)	100.00%	100.00%								83.70%	80.60%			13.80%	16.50%					2.50%	2.90%
Fixed Rate (as a percent)								12.25%	13.02%			12.00%	12.96%			10.10%	0.00%					13.11%	13.11%
Spread over LIBOR (as a percent)								6.98%	7.97%			6.47%	6.86%			13.70%	14.19%					0.00%	0.00%
Unleveraged Current Yield (as a percent)								7.61%	8.43%			6.58%	7.26%			13.79%	14.27%					13.24%	13.24%
Floating Rate as % of Principal Amount (percent)	95.70%	92.40%								99.00%	94.60%			93.40%	100.00%					0.00%	0.00%
Future funding commitments																		59,300,000	44,600,000
Proportionate interest in debt instrument, including future funding commitments																														69,200,000
Principal amount of investments financed by borrowings															17,500,000
Carrying value served as collateral			251,700,000	30,900,000		701,700,000	711,500,000
Restricted cash	123,585,000	223,002,000			42,600,000	800,000
Face amount of investment	$ 981,300,000																							$ 898,200,000
Variable rate on basis floor (percent)																									0.89%	1.07%