NOTES RECEIVABLE, PREFERRED EQUITY, AND OTHER REAL ESTATE RELATED INVESTMENTS Schedule of Notes Receivable (Details) (USD $)	1 Months Ended	12 Months Ended					1 Months Ended
	Sep. 30, 2014	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012	Apr. 30, 2014	Jul. 31, 2014	Oct. 31, 2014	Jan. 31, 2014	Dec. 31, 2011	May 31, 2014
Mortgage Loans on Real Estate [Line Items]
Net carrying amount of notes receivable		$ 102,286,000		$ 126,656,000		$ 129,278,000					$ 59,989,000
Proceeds from notes receivable	1,900,000	18,095,000		29,583,000		25,388,000
Collections of principal	1,200,000	18,095,000		29,583,000		25,388,000
New investments		31,169,000		45,000,000		108,629,000
Collections of interest	700,000
152 - 154 Spring Street [Member]
Mortgage Loans on Real Estate [Line Items]
Exchange of mortgage for investment							38,000,000
First Mortgage, 7.7% Loan Due 2015 [Member]
Mortgage Loans on Real Estate [Line Items]
Effective interest rate		7.70%	[1]
First Priority Liens		0
Net carrying amount of notes receivable		12,000,000		12,000,000
Mezzanine Loan, 12.7% Loan, Due 2015 [Member]
Mortgage Loans on Real Estate [Line Items]
Effective interest rate		12.70%	[1]				12.70%
First Priority Liens		18,900,000
Net carrying amount of notes receivable		8,000,000		0
Proceeds from notes receivable							13,000,000	5,000,000
First Mortgage Loan, 8.8% Loan, Due 2015 [Member]
Mortgage Loans on Real Estate [Line Items]
Effective interest rate		8.80%	[1]						8.80%
First Priority Liens		0
Net carrying amount of notes receivable		7,500,000		0
Number of loan extensions		1
Length of loan extension		12 months
New investments									7,500,000
Zero Coupon Loan, 24% Loan, Due 2016 [Member]
Mortgage Loans on Real Estate [Line Items]
Effective interest rate		24.00%	[1],[2]
First Priority Liens		166,200,000	[2]
Net carrying amount of notes receivable		4,986,000	[2]	4,431,000	[2]
Number of cross-collateralized loans		3
Number of borrowers		1
First Mortgage Loan, 5.5% Loan Due 2016 [Member]
Mortgage Loans on Real Estate [Line Items]
Effective interest rate		5.50%	[1]
First Priority Liens		0
Net carrying amount of notes receivable		4,000,000		42,000,000
Number of loan extensions		1
Length of loan extension		6 months
Preferred Equity, 13.5% Loan, Due 2016 [Member]
Mortgage Loans on Real Estate [Line Items]
Effective interest rate		13.50%	[1]									13.50%
First Priority Liens		0
Net carrying amount of notes receivable		4,000,000		0								4,000,000
Other Loan, 18% Loan, Due 2017 [Member]
Mortgage Loans on Real Estate [Line Items]
Effective interest rate		18.00%	[1]					18.00%
First Priority Liens		0
Net carrying amount of notes receivable		3,307,000		0				4,800,000
Preferred Equity, 8.1% Loan, Due 2017 [Member]
Mortgage Loans on Real Estate [Line Items]
Effective interest rate		8.10%	[1]
First Priority Liens		20,855,000
Net carrying amount of notes receivable		13,000,000		13,000,000
Mezzanine, 15% Due 2020 [Member]
Mortgage Loans on Real Estate [Line Items]
Effective interest rate		15.00%	[1]
First Priority Liens		0
Net carrying amount of notes receivable		30,879,000		30,879,000
First Mortgage Loan, 8.0% Loan, Due On Demand [Member]
Mortgage Loans on Real Estate [Line Items]
Effective interest rate		6.00%	[1]
First Priority Liens		0
Net carrying amount of notes receivable		0		6,400,000
Proceeds from notes receivable										6,400,000
Other Loan, 2.5% LIBOR Loan, Due 2020 [Member]
Mortgage Loans on Real Estate [Line Items]
Basis spread on variable rate		2.50%	[1]
First Priority Liens		0
Net carrying amount of notes receivable		4,000,000		3,000,000				4,000,000
New investments								1,000,000
Mezzanine Loan, 10.0% Loan, Due On Demand [Member]
Mortgage Loans on Real Estate [Line Items]
Effective interest rate		10.00%	[1],[3]
First Priority Liens		87,477,000	[3]
Net carrying amount of notes receivable		7,983,000	[3]	9,089,000	[3]
Mezzanine Loan, 15.0% Loan, Due Upon Capital Event [Member]
Mortgage Loans on Real Estate [Line Items]
Effective interest rate		15.00%	[1]
First Priority Liens		16,668,000
Net carrying amount of notes receivable		0		3,834,000
Individually Less Than 3%, Variable Interest Rate Due 2014 to Capital Event [Member]
Mortgage Loans on Real Estate [Line Items]
First Priority Liens		0	[4]
Net carrying amount of notes receivable		2,631,000	[4]	2,023,000	[4]
Number of loans		3
Individually Less Than 3%, Variable Interest Rate Due 2014 to Capital Event [Member] | Minimum [Member]
Mortgage Loans on Real Estate [Line Items]
Basis spread on variable rate		2.70%	[1],[4]
Individually Less Than 3%, Variable Interest Rate Due 2014 to Capital Event [Member] | Maximum [Member]
Mortgage Loans on Real Estate [Line Items]
Basis spread on variable rate		17.50%	[1],[4]
Mortgage Loan, LIBOR Plus 13.75% Loan, Due 2024 [Member]
Mortgage Loans on Real Estate [Line Items]
Basis spread on variable rate							3.75%
Net carrying amount of notes receivable							1,900,000
Mezzanine Loan [Member]
Mortgage Loans on Real Estate [Line Items]
Net carrying amount of notes receivable							8,300,000
Proceeds from notes receivable							10,300,000			1,400,000
Collections of principal										700,000
Gain (loss) on sale of notes receivable										700,000
Write-down or reserve, amount		$ 2,000,000

[1] Includes origination and exit fees

[2] The principal balance for this accrual-only loan is increased by the interest accrued

[3] Comprised of three cross-collateralized loans from one borrower, which are non-performing

[4] Consists of three loans as of December 31, 2014