DEBT (Details) - USD ($)	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Secured and Unsecured Debt [Line Items]
Repayments of Bank Debt	$ 282,802,000	$ 161,618,000
Unsecured bank credit facilities, change during period	(114,321,000)
Proceeds from unsecured bank credit facilities	168,283,000	$ 195,545,000
Loans Payable, Noncurrent [Abstract]
Secured Debt	340,730,000		$ 350,285,000
Unsecured Debt	592,674,000		528,210,000
Unsecured bank credit facilities	35,093,000		149,414,000
Total debt	968,497,000		1,027,909,000
Secured Debt [Member]
Secured and Unsecured Debt [Line Items]
Secured debt, change during period	(9,555,000)
Secured debt, principal payments during period	9,376,000
Secured and unsecured debt [Member]
Payments of principal over future years [Abstract]
Remainder of 2016	83,412,000
2017	58,239,000
2018	141,316,000
2019	130,569,000
2020	114,097,000
2021 and beyond	409,375,000
Long-term debt, maturities, secured debt and unsecured debt	937,008,000
Unsecured Debt [Member]
Secured and Unsecured Debt [Line Items]
Unsecured debt, change during period	64,464,000
Sixty-five million term loan (2016) [Member]
Secured and Unsecured Debt [Line Items]
Unsecured debt, notional amount	$ 65,000,000
Unsecured debt, term (in years)	7
Interest Rate (in hundredths)	2.863%
Long-term debt, margin over LIBOR rate	1.65%
Secured Debt [Member]
Loans Payable, Noncurrent [Abstract]
Secured debt, carrying amount	$ 342,008,000		351,401,000
Unamortized debt issuance costs	(1,278,000)		(1,116,000)
Secured Debt	340,730,000		350,285,000
Unsecured Debt [Member]
Loans Payable, Noncurrent [Abstract]
Unsecured debt, carrying amount	595,000,000		530,000,000
Unamortized debt issuance costs	(2,326,000)		(1,790,000)
Unsecured Debt	592,674,000		528,210,000
Unsecured bank credit facilities
Loans Payable, Noncurrent [Abstract]
Unsecured bank credit facilities, carrying amount	36,317,000		150,836,000
Unamortized debt issuance costs	(1,224,000)		(1,422,000)
Unsecured bank credit facilities	$ 35,093,000		$ 149,414,000