ORGANIZATION (Details) $ in Thousands	3 Months Ended	12 Months Ended	35 Months Ended	119 Months Ended
	Mar. 31, 2018 USD ($) loans-receivable property shares	Dec. 31, 2017 USD ($) shares	Mar. 22, 2011 USD ($) shares	Mar. 31, 2018 USD ($) loans-receivable property shares
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%
Number of real estate loans receivable | loans-receivable	1			1
Issuance of common stock, value | $			$ 1,800,000
Shares of common stock sold under dividend reinvestment plan, value | $				$ 298,200
Redemptions of common stock | $	$ 1,277	$ 5,767
Common Stock
Organizational Structure [Line Items]
Issuance of common stock, shares | shares			182,681,633
Shares of common stock sold under dividend reinvestment plan, shares | shares				30,903,504
Redemptions of common stock (in shares) | shares	(261,092)	(1,053,650)		(26,199,927)
Redemptions of common stock | $	$ 3	$ 10		$ 247,100
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 | shares	20,000			20,000
Office Properties
Organizational Structure [Line Items]
Number of real estate properties | property	8			8
Office Campus
Organizational Structure [Line Items]
Number of real estate properties | property	1			1
Office Buildings, Campus
Organizational Structure [Line Items]
Number of real estate properties | property	8			8
Office Buildings, Campus | Held-for-sale
Organizational Structure [Line Items]
Number of real estate properties | property	2			2