ORGANIZATION (Details)	3 Months Ended
	Mar. 31, 2020 numberOfProperties shares	Jan. 31, 2020 shares	Dec. 31, 2019 shares	Mar. 31, 2019 shares	Dec. 31, 2018 shares
Organizational Structure [Line Items]
Common stock, shares issued (in shares)	185,062,935		185,302,037
Common stock, shares outstanding (in shares)	185,062,935		185,302,037
Common Stock
Organizational Structure [Line Items]
Common stock, shares outstanding (in shares)		185,228,220	185,302,037	186,188,796	186,464,794
KBS Capital Advisors LLC
Organizational Structure [Line Items]
Period of Advisory Agreement renewal	1 year
Period of termination notice	60 days
KBS Capital Advisors LLC |  Common Stock
Organizational Structure [Line Items]
Shares held by affiliate	20,000
Office Properties
Organizational Structure [Line Items]
Number of real estate properties | numberOfProperties	4
Office Campus
Organizational Structure [Line Items]
Number of real estate properties | numberOfProperties	1
Office Buildings, Campus
Organizational Structure [Line Items]
Number of real estate properties | numberOfProperties	5
KBS Limited Partnership II
Organizational Structure [Line Items]
Partnership interest in Operating Partnership	0.10%
Partnership interest in the Operating Partnership and is its sole limited partner	99.90%