MORTGAGE LOAN RECEIVABLES - Schedule of Mortgage Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Mortgage Loans on Real Estate [Line Items]
Outstanding Face Amount	$ 2,321,194	$ 1,954,878
Provision for loan losses	(3,700)	(3,100)	$ (2,500)	$ (1,900)
Carrying Value	2,310,409	1,939,008
Mortgage loan receivables held for investment, at amortized cost
Mortgage Loans on Real Estate [Line Items]
Outstanding Face Amount	1,749,556	1,536,923
Carrying Value, gross	1,742,345	1,524,153
Provision for loan losses	(3,700)	(3,100)
Carrying Value	$ 1,738,645	$ 1,521,053
Weighted Average Yield (as a percent)	7.56%	7.33%
Remaining Maturity (years)	1 year 4 months 17 days	1 year 11 months 15 days
Mortgage loan receivables held for sale
Mortgage Loans on Real Estate [Line Items]
Outstanding Face Amount	$ 571,638	$ 417,955
Carrying Value	$ 571,764	$ 417,955
Weighted Average Yield (as a percent)	4.56%	4.31%
Remaining Maturity (years)	6 years 2 months 12 days	9 years 8 months 19 days