Derivative Instruments, Weighted-Average Fix Pay Rate

No definition available.

Name:	kbsriii_DerivativeInstrumentsWeightedAverageFixPayRate
Namespace Prefix:	kbsriii_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Derivative Instruments, Weighted-Average Remaining Term in Years

+ References

No definition available.

+ Details

Name:	kbsriii_DerivativeInstrumentsWeightedAverageRemainingTerminYears
Namespace Prefix:	kbsriii_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Derivative, Number of Instruments Terminated

+ References

No definition available.

+ Details

Name:	kbsriii_DerivativeNumberOfInstrumentsTerminated
Namespace Prefix:	kbsriii_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Gain (loss) on Settlement of Early Terminated Swaps

+ References

No definition available.

+ Details

Name:	kbsriii_GainLossOnSettlementOfEarlyTerminatedSwaps
Namespace Prefix:	kbsriii_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The percentage points added to the reference rate to compute the variable rate on the interest rate derivative.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeBasisSpreadOnVariableRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Fixed interest rate related to the interest rate derivative.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeFixedInterestRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480237/815-40-50-5

+ Details

Name:	us-gaap_DerivativeLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-1B

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-1A

+ Details

Name:	us-gaap_DerivativeNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of derivative instruments of a particular group held by the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 210
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478795/946-210-50-6

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 946
-SubTopic 210
-Name Accounting Standards Codification
-Section 55
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477439/946-210-55-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 5
-Subparagraph (SX 210.12-13(Column A)(Footnote 3))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477271/946-320-S99-5

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 5
-Subparagraph (SX 210.12-13(Column C))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477271/946-320-S99-5

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 5A
-Subparagraph (SX 210.12-13A(Column B))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477271/946-320-S99-5A

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-1B

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-1A

+ Details

Name:	us-gaap_DerivativeNumberOfInstrumentsHeld
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=kbsriii_SecuredOvernightFinancingRateSOFRFallbackMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=kbsriii_LondonInterbankOfferedRateLIBOR1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_SecuredOvernightFinancingRateSofrMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateCapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

DERIVATIVE INSTRUMENTS - Schedule of Notional Amount and Other Information Related to the Interest Rate Swaps and Interest Rate Cap (Details)	1 Months Ended	12 Months Ended
	Feb. 29, 2024 USD ($) investment_instrument	Dec. 31, 2024 USD ($) investment_instrument	Dec. 31, 2023 USD ($) investment_instrument	Dec. 31, 2022 USD ($)	Jun. 30, 2023 investment_instrument
Derivative [Line Items]
Gain (loss) on settlement of early terminated swaps \| $		$ (6,552,000)	$ 0	$ 0
Interest rate swaps \| Derivative instruments not designated as hedging instruments
Derivative [Line Items]
Number of Instruments		14	16
Notional Amount \| $		$ 1,100,000,000	$ 1,300,000,000
Weighted-Average Fix Pay Rate		3.10%
Weighted-Average Remaining Term in Years		1 year 4 months 24 days
Derivative, number of instruments terminated	2	2
Gain (loss) on settlement of early terminated swaps \| $	$ 6,600,000	$ 6,600,000
Interest rate swaps \| Derivative instruments not designated as hedging instruments \| Secured Overnight Financing Rate (SOFR) Fallback
Derivative [Line Items]
Number of Instruments		2
Derivative, basis spread on variable rate					0.11448%
Interest rate swaps \| Derivative instruments not designated as hedging instruments \| One-month LIBOR
Derivative [Line Items]
Number of Instruments					8
Interest rate swaps \| Derivative instruments not designated as hedging instruments \| Minimum \| Secured Overnight Financing Rate (SOFR) Fallback
Derivative [Line Items]
Reference rate		1.08%
Interest rate swaps \| Derivative instruments not designated as hedging instruments \| Minimum \| One-month SOFR
Derivative [Line Items]
Reference rate		2.38%
Interest rate swaps \| Derivative instruments not designated as hedging instruments \| Maximum \| Secured Overnight Financing Rate (SOFR) Fallback
Derivative [Line Items]
Reference rate		1.28%
Interest rate swaps \| Derivative instruments not designated as hedging instruments \| Maximum \| One-month SOFR
Derivative [Line Items]
Reference rate		3.92%
Interest rate cap \| Derivative instruments not designated as hedging instruments
Derivative [Line Items]
Number of Instruments		0	1
Notional Amount \| $		$ 0	$ 125,000,000