DEBT (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Debt
Gross debt	$ 664,912,000
Total Debt	664,094,000	$ 608,714,000
Mortgages Payable
Debt
Gross debt	145,842,000	221,847,000
Premiums and discounts on assumed mortgages	1,292,000	1,961,000
Total Debt	$ 147,134,000	223,808,000
Mortgage loan with a fixed interest of 7.66% per annum, due on December 1, 2015
Debt
Gross debt		$ 26,783,000
Fixed interest rate (as a percent)	7.66%	7.66%
Period of amortization schedule	20 years	20 years
Amount of balance due on maturity	$ 25,324,000	$ 25,324,000
Mortgage loan with a fixed interest of 4.50% per annum, due on January 5, 2027
Debt
Gross debt	$ 46,000,000	$ 46,000,000
Fixed interest rate (as a percent)	4.50%	4.50%
Period of amortization schedule	10 years	10 years
Amount of balance due on maturity	$ 42,008,000	$ 42,008,000
Mortgage loan with a fixed interest of 5.56% per annum, due on July 1, 2015
Debt
Gross debt		$ 12,442,000
Fixed interest rate (as a percent)	5.56%	5.56%
Period of amortization schedule	10 years	10 years
Amount of balance due on maturity		$ 12,288,000
Mortgage loan with a fixed interest of 6.65% per annum, due on July 15, 2018
Debt
Gross debt	$ 29,937,000	$ 32,070,000
Fixed interest rate (as a percent)	6.65%	6.65%
Period of amortization schedule	25 years	25 years
Amount of balance due on maturity	$ 21,136,000	$ 21,136,000
Mortgage loan with a fixed interest of 5.06% per annum, due on September 1, 2015
Debt
Gross debt		$ 33,734,000
Fixed interest rate (as a percent)	5.06%	5.06%
Amount of balance due on maturity	$ 33,068,000	$ 33,068,000
Mortgage loan with a fixed interest of 5.39% per annum, due on March 1, 2021
Debt
Gross debt	$ 40,021,000	$ 40,526,000
Fixed interest rate (as a percent)	5.39%	5.39%
Amount of balance due on maturity	$ 35,695,000	$ 35,695,000
Mortgage loan with a fixed interest of 5.18% per annum, due on June 5, 2021
Debt
Gross debt	$ 29,884,000	$ 30,292,000
Fixed interest rate (as a percent)	5.18%	5.18%
Amount of balance due on maturity	$ 26,232,000	$ 26,232,000
Other debt
Debt
Gross debt	519,070,000	387,070,000
Total Debt	516,960,000	384,906,000
Junior subordinated notes
Debt
Gross debt	27,070,000	27,070,000
Premiums and discounts on assumed mortgages	$ (2,110,000)	$ (2,164,000)
Junior subordinated notes | LIBOR
Debt
Interest rate margin (as a percent)	3.25%	3.25%
Unsecured credit facilities
Debt
Gross debt	$ 492,000,000	$ 360,000,000