MORTGAGE LOAN RECEIVABLES - Schedule of Mortgage Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Mortgage Loans on Real Estate [Line Items]
Outstanding Face Amount	$ 2,371,827	$ 2,321,194
Provision for loan losses	(4,000)	(3,700)	$ (3,100)	$ (2,500)
Carrying Value	$ 2,353,977	$ 2,310,409
Weighted Average Yield (as a percent)	6.73%	6.83%
Remaining Maturity (years)	2 years 1 month 6 days	2 years 6 months 29 days
Mortgage loan receivables held for investment, at amortized cost
Mortgage Loans on Real Estate [Line Items]
Outstanding Face Amount	$ 2,011,309	$ 1,749,556
Carrying Value, gross	2,000,095	1,742,345
Provision for loan losses	(4,000)	(3,700)
Carrying Value	$ 1,996,095	$ 1,738,645
Weighted Average Yield (as a percent)	7.17%	7.56%
Remaining Maturity (years)	1 year 7 months 28 days	1 year 4 months 17 days
Mortgage loan receivables held for sale
Mortgage Loans on Real Estate [Line Items]
Outstanding Face Amount	$ 360,518	$ 571,638
Carrying Value	$ 357,882	$ 571,764
Weighted Average Yield (as a percent)	4.20%	4.56%
Remaining Maturity (years)	4 years 6 months 18 days	6 years 2 months 12 days