SIGNIFICANT ACCOUNTING POLICIES (Details 2) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Depreciation	$ 76,007,000	$ 69,010,000	$ 63,793,000
Percentage of Occupation When Development Cost Ceased Being Capitalized	90.00%	80.00%
Length of Time After Project Completion When Development Cost Ceased Being Capitalized	1 year	1 year
Buildings [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	40 years
Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	3 years
Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	15 years
Accounting Standards Update 2016-02 [Member]
Property, Plant and Equipment [Line Items]
Right of use asset and lease liability for ground leases and office leases, estimated percentage of Total assets	less than 1%
Lease costs that are expected to be expensed after adoption of new accounting standard	$ 200,000