DEBT (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Secured and Unsecured Debt [Line Items]
Repayments of Bank Debt	$ 60,309,000	$ 124,972,000
Unsecured bank credit facilities, change during period	16,435,000
Proceeds from unsecured bank credit facilities	76,646,000	$ 139,931,000
Loans Payable, Noncurrent [Abstract]
Secured Debt	345,444,000		$ 350,285,000
Unsecured Debt	528,312,000		528,210,000
Unsecured bank credit facilities	165,849,000		149,414,000
Total debt	1,039,605,000		1,027,909,000
Secured Debt [Member]
Secured and Unsecured Debt [Line Items]
Secured debt, change during period	(4,841,000)
Secured debt, principal payments during period	4,656,000
Secured and unsecured debt [Member]
Payments of principal over future years [Abstract]
Remainder of 2016	88,142,000
2017	58,239,000
2018	141,316,000
2019	130,569,000
2020	114,097,000
2021 and beyond	344,374,000
Secured Debt [Member]
Loans Payable, Noncurrent [Abstract]
Secured debt, carrying amount	346,737,000		351,401,000
Unamortized debt issuance costs	(1,293,000)		(1,116,000)
Secured Debt	345,444,000		350,285,000
Unsecured Debt [Member]
Loans Payable, Noncurrent [Abstract]
Unsecured debt, carrying amount	530,000,000		530,000,000
Unamortized debt issuance costs	(1,688,000)		(1,790,000)
Unsecured Debt	528,312,000		528,210,000
Unsecured bank credit facilities
Loans Payable, Noncurrent [Abstract]
Unsecured bank credit facilities, carrying amount	167,173,000		150,836,000
Unamortized debt issuance costs	(1,324,000)		(1,422,000)
Unsecured bank credit facilities	$ 165,849,000		$ 149,414,000