ORGANIZATION (Details) $ in Thousands							1 Months Ended	6 Months Ended	12 Months Ended	36 Months Ended	103 Months Ended
	Mar. 08, 2016 USD ($)	Mar. 08, 2016 ILS (₪)	Mar. 08, 2016 ILS (₪)	Mar. 07, 2016 ILS (₪)	Mar. 02, 2016 ILS (₪)	Mar. 01, 2016 ILS (₪)	Dec. 31, 2017 USD ($) shares	Jun. 30, 2018 USD ($) a portfolio property investment shares	Dec. 31, 2017 USD ($) shares	Nov. 14, 2012 USD ($) shares	Jun. 30, 2018 USD ($) a portfolio property investment shares	Dec. 18, 2015 shares	Oct. 23, 2012 USD ($) shares	Dec. 29, 2011 USD ($) shares	Jan. 08, 2009 shares
Organizational Structure [Line Items]
Common stock, shares authorized (in shares)							1,000,000,000	1,000,000,000	1,000,000,000		1,000,000,000
Common stock, shares issued (in shares)							52,053,817	54,682,660	52,053,817		54,682,660		55,249	220,994
Partnership interest in Operating Partnership								0.10%
Partnership interest in the Operating Partnership and is its sole limited partner								99.90%
Issuance of common stock, value | $								$ 964	$ 8,666	$ 561,700
Shares of common stock sold under dividend reinvestment plan, value | $											$ 75,000
Redemptions of common stock | $								115,071	74,780		266,900
Common stock, value, issued | $							$ 521	$ 547	$ 521		$ 547		$ 500	$ 2,000
Number of investments in unconsolidated joint venture | investment								3			3
Number of investments in debt securities | investment								1			1
Number of investments in equity securities | investment								3			3
Held-for-sale
Organizational Structure [Line Items]
Number of real estate properties | property								1			1
Office Properties
Organizational Structure [Line Items]
Number of real estate properties consolidated | property								7			7
Number of real estate properties | property								6			6
Office Properties | Held-for-sale
Organizational Structure [Line Items]
Number of real estate properties | property								1			1
Office Portfolio
Organizational Structure [Line Items]
Number of real estate properties | portfolio								1			1
Office Buildings, Portfolio
Organizational Structure [Line Items]
Number of real estate properties | property								4			4
Undeveloped Land, Portfolio
Organizational Structure [Line Items]
Real estate area of undeveloped land | a								14			14
Office/Flex/Industrial Portfolio
Organizational Structure [Line Items]
Number of real estate properties | property								1			1
Office/Flex/Industrial Buildings
Organizational Structure [Line Items]
Number of real estate properties | property								21			21
Retail Property, Portfolio
Organizational Structure [Line Items]
Number of real estate properties | property								1			1
Undeveloped Land
Organizational Structure [Line Items]
Real estate area of undeveloped land | a								1,100			1,100
Number of investments in real estate | investment								3			3
Series A Debentures | Bonds Payable
Organizational Structure [Line Items]
Maximum borrowing capacity (in shares) | ₪					₪ 1,000,000,000
Contractual interest rate, percentage					4.25%
Proceeds from issuance of debt	$ 249,200	₪ 970,200,000	₪ 970,200,000	₪ 127,700,000		₪ 842,500,000
Principal installment payments required as percent of total debt					20.00%
Special Dividends
Organizational Structure [Line Items]
Common stock, shares issued (in shares)								13,069,487			13,069,487
Maximum | Series A Debentures | Bonds Payable
Organizational Structure [Line Items]
Contractual interest rate, percentage					4.25%
Common Stock
Organizational Structure [Line Items]
Shares registered in primary offering (in shares)															100,000,000
Shares registered for sale under dividend reinvestment plan (in shares)															40,000,000
Issuance of common stock (in shares)								83,855	585,192	56,584,976
Issuance of common stock, value | $								$ 1	$ 6
Shares of common stock sold under dividend reinvestment plan, (in shares)											6,704,217
Redemptions of common stock (in shares)								10,524,499	5,307,142		21,972,263
Redemptions of common stock | $							$ 4,400	$ 105	$ 53
Common Stock | Minimum
Organizational Structure [Line Items]
Stock offering, shares authorized for issuance (in shares)															250,000
Common Stock | Maximum
Organizational Structure [Line Items]
Stock offering, shares authorized for issuance (in shares)															140,000,000
KBS Strategic Opportunity BVI
Organizational Structure [Line Items]
Common stock, shares authorized (in shares)												50,000
KBS Strategic Opportunity BVI | Operating Partnership
Organizational Structure [Line Items]
Common stock, shares issued (in shares)												10,000