DEBT - Schedule (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Debt
Total Debt	$ 656,498,000	$ 656,835,000
Deferred loan costs, gross	10,445,000	10,445,000
Deferred loan costs, accumulated amortization	5,158,000	4,332,000
Mortgages Payable
Debt
Gross debt	143,723,000	144,791,000
Deferred loan costs	(862,000)	(897,000)
Premiums and discounts	1,064,000	1,178,000
Total Debt	143,925,000	145,072,000
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 6.65% per annum, due on July 15, 2018
Debt
Gross debt	$ 28,451,000	$ 29,201,000
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 5.39% per annum, due on March 1, 2021
Debt
Gross debt	$ 39,669,000	$ 39,846,000
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	$ 29,603,000	$ 29,744,000
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	519,070,000
Total Debt	512,573,000	511,763,000
Unsecured term loan and credit facilities
Debt
Deferred loan costs	(4,425,000)	(5,216,000)
Junior subordinated notes
Debt
Gross debt	27,070,000	27,070,000
Premiums and discounts	$ (2,072,000)	$ (2,091,000)
Junior subordinated notes | LIBOR
Debt
Interest rate margin (as a percent)	3.25%	3.25%
Unsecured term loan facility
Debt
Gross debt	$ 385,000,000	$ 385,000,000
Unsecured credit facilities
Debt
Gross debt	$ 107,000,000	$ 107,000,000