ORGANIZATION (Details)		3 Months Ended		6 Months Ended		50 Months Ended	65 Months Ended
	Aug. 11, 2015 USD ($) shares	Jun. 30, 2020 USD ($) numberOfProperties numberOfInvestments shares	Jun. 30, 2019 USD ($) shares	Jun. 30, 2020 USD ($) numberOfProperties numberOfInvestments shares	Jun. 30, 2019 USD ($) shares	Jun. 30, 2020 USD ($) numberOfProperties numberOfInvestments shares	Jun. 30, 2020 USD ($) numberOfProperties numberOfInvestments shares	Dec. 31, 2019 shares	Oct. 03, 2017 shares	Jun. 11, 2015 shares	Feb. 04, 2015 USD ($)	Jan. 27, 2015 $ / shares shares
Organizational Structure [Line Items]
Number of investments in unconsolidated joint venture | numberOfInvestments		1		1		1	1
Core property, minimum percent of occupancy		80.00%		80.00%		80.00%	80.00%
Issuance of common stock | $		$ 190,000	$ 1,441,000	$ 459,000	$ 3,108,000
Redemptions of common stock | $		$ 200,000		$ 200,000	$ 21,000
Percent of total rental income from retail tenants		500.00%
Class A Common Stock
Organizational Structure [Line Items]
Common stock, shares issued (in shares)		9,867,625		9,867,625		9,867,625	9,867,625	9,841,004
Class T Common Stock
Organizational Structure [Line Items]
Common stock, shares issued (in shares)		310,418		310,418		310,418	310,418	306,292
Maximum | Class A Common Stock | Second Private Placement
Organizational Structure [Line Items]
Shares authorized for issuance									1,000,000,000
Common Stock | Public Offering
Organizational Structure [Line Items]
Issuance of common stock | $							$ 3,900,000
Stock issued during period, dividend reinvestment plan | $							$ 8,400,000
Common Stock | Class A Common Stock
Organizational Structure [Line Items]
Shares authorized for dividend reinvestment plan										5,000,000
Issuance of common stock (in shares)	46,362	20,846	153,245	50,357	331,202
Issuance of common stock | $	$ 300,000	$ 0	$ 1,000	$ 1,000	$ 3,000
Redemptions of common stock (in shares)		23,736		23,736	0		446,022
Redemptions of common stock | $					$ 0		$ 3,700,000
Common Stock | Class A Common Stock | Private Placement
Organizational Structure [Line Items]
Issuance of common stock (in shares)						8,548,972
Issuance of common stock | $						$ 76,800,000
Stock issued during period, dividend reinvestment plan (in shares)						74,744
Stock issued during period, dividend reinvestment plan | $						$ 700,000
Common Stock | Class A Common Stock | Public Offering
Organizational Structure [Line Items]
Issuance of common stock (in shares)							122,721
Stock issued during period, dividend reinvestment plan (in shares)							876,321
Common Stock | Class A Common Stock | Second Private Offering
Organizational Structure [Line Items]
Issuance of common stock (in shares)						612,272
Issuance of common stock | $						$ 5,500,000
Common Stock | Class T Common Stock
Organizational Structure [Line Items]
Issuance of common stock (in shares)		1,706	3,392	4,126	6,688
Redemptions of common stock (in shares)		0		0	2,245		2,245
Common Stock | Class T Common Stock | Public Offering
Organizational Structure [Line Items]
Issuance of common stock (in shares)							270,415
Stock issued during period, dividend reinvestment plan (in shares)							40,474
Common Stock | Maximum
Organizational Structure [Line Items]
Shares authorized for issuance, value | $											$ 1,500,000,000
Shares authorized for dividend reinvestment plan | $											$ 800,000,000
Common Stock | Maximum | Class A Common Stock
Organizational Structure [Line Items]
Shares authorized for issuance										105,000,000
Office Building
Organizational Structure [Line Items]
Number of real estate properties | numberOfProperties		3		3		3	3
KBS Capital Advisors LLC
Organizational Structure [Line Items]
Common stock, shares issued (in shares)												20,000
Purchase price per share (in usd per share) | $ / shares												$ 10.00
KBS Growth & Income Limited Partnership
Organizational Structure [Line Items]
Managing member or general partner, ownership interest				0.10%
Members or limited partners, ownership interest				99.90%