RELATED PARTY TRANSACTIONS (Subordinated Performance Fee Due Upon Termination) (Details) - KBS Capital Advisors LLC - Subordinated Performance Fee Due Upon Termination	12 Months Ended
Dec. 31, 2019 shares
Related Party Transaction [Line Items]
Shares to be awarded (in shares)	3,411,737
Period of redemption after vesting	60 days
Termination fee as percent of liquidation proceeds	50.00%
Percent of total operating expenses in four consecutive quarters	2.00%
Percent of total operating expenses, benchmark	25.00%
Maximum ratio for number of remaining shares to be redeemed	0.006667
After November 1, 2024
Related Party Transaction [Line Items]
Period of redemption of remaining shares	60 days

Number of shares issued during the period related to Restricted Stock Awards, net of any shares forfeited.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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