REAL ESTATE SOLD AND HELD FOR SALE DISCONTINUED OPERATIONS (Details)	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($) ft²	Sep. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Sep. 30, 2018 USD ($) ft² a	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) ft² a Integer
Long Lived Assets Held-for-sale [Line Items]
Gains (Losses) on Sales of Investment Real Estate	$ 4,051,000	$ 0		$ 14,273,000	$ 21,855,000
Number of real estate properties transferred to held for sale and sold | Integer						2
2017 Operating Property Sales [Member]
Long Lived Assets Held-for-sale [Line Items]
Square Footage of Real Estate Property | ft²						514,000
Gain (Loss) on Sale of Properties						$ 21,900,000
Proceeds from Sale of Property, Plant, and Equipment						$ 38,000,000
2018 Operating Property Sales [Member]
Long Lived Assets Held-for-sale [Line Items]
Square Footage of Real Estate Property | ft²	339,000			339,000
Gain (Loss) on Sale of Properties	$ 4,100,000			$ 14,300,000
Proceeds from Sale of Property, Plant, and Equipment				$ 22,900,000
Land [Member]
Long Lived Assets Held-for-sale [Line Items]
SIze (in acres) of land sold | a				11		19
Proceeds from Sale of Property, Plant, and Equipment				$ 2,600,000		$ 3,800,000
Loss on sales of land			$ (40,000)
Gain on sales of land				$ 86,000		$ 293,000