Additional One Unit Acquired Per Number of Units Held

No definition available.

Name:	kbsriii_AdditionalOneUnitAcquiredPerNumberOfUnitsHeld
Namespace Prefix:	kbsriii_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of Real Estate Properties Disposed.

+ References

No definition available.

+ Details

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

- Definition

Units Acquired, Price per Unit

+ References

No definition available.

+ Details

Name:	kbsriii_UnitsAcquiredPricePerUnit
Namespace Prefix:	kbsriii_
Data Type:	dtr-types1:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Units Acquired, Units

+ References

No definition available.

+ Details

Name:	kbsriii_UnitsAcquiredUnits
Namespace Prefix:	kbsriii_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Units Acquired, Value

+ References

No definition available.

+ Details

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

- Definition

Units, Closing Price

+ References

No definition available.

+ Details

Name:	kbsriii_UnitsClosingPrice
Namespace Prefix:	kbsriii_
Data Type:	dtr-types1:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Units Disposed, Unit

+ References

No definition available.

+ Details

Name:	kbsriii_UnitsDisposedUnit
Namespace Prefix:	kbsriii_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Units Disposed, Value

+ References

No definition available.

+ Details

Name:	kbsriii_UnitsDisposedValue
Namespace Prefix:	kbsriii_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Units Held, Units

+ References

No definition available.

+ Details

Name:	kbsriii_UnitsHeldUnits
Namespace Prefix:	kbsriii_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Units Investments, Unit

+ References

No definition available.

+ Details

Name:	kbsriii_UnitsInvestmentsUnit
Namespace Prefix:	kbsriii_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of dividend income on investment in equity security, classified as operating.

+ References

No definition available.

+ Details

Name:	us-gaap_DividendIncomeEquitySecuritiesOperating
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 80
-Name Accounting Standards Codification
-Section 55
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480078/944-80-55-14

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 80
-Name Accounting Standards Codification
-Section 55
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480078/944-80-55-9

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482736/825-10-45-1A

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1)(6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

+ Details

Name:	us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of unrealized loss on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 321
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479536/321-10-50-4

+ Details

Name:	us-gaap_EquitySecuritiesFvNiUnrealizedLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percentage of subsidiary's or equity investee's stock owned by parent company after stock transaction.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockPercentageOfOwnershipAfterTransaction
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- 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 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-28

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

+ Details

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

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=kbsriii_SREITMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=kbsriii_SREITMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DisposalGroupClassificationAxis=us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

REAL ESTATE EQUITY SECURITIES (Details) $ / shares in Units, $ in Thousands							1 Months Ended		3 Months Ended		12 Months Ended
	Mar. 28, 2024 shares	Mar. 04, 2024 shares	Nov. 09, 2021 USD ($) shares	Aug. 21, 2019 USD ($) shares	Jul. 19, 2019 USD ($) $ / shares shares	Jul. 18, 2019 property	Nov. 30, 2024 property	Feb. 29, 2024 property	Mar. 31, 2025 USD ($) $ / shares shares	Mar. 31, 2024 USD ($)	Dec. 31, 2024 USD ($) property
Schedule of Equity Method Investments [Line Items]
Real estate equity securities									$ 35,377		$ 40,600
Dividend income from real estate equity securities									$ 261	$ 540
SREIT
Schedule of Equity Method Investments [Line Items]
Units acquired (in shares) \| shares					307,953,999
Units acquired					$ 271,000
Units acquired (in dollars per share) \| $ / shares					$ 0.88
Ownership percentage after transaction			18.50%	31.30%	33.30%				18.20%
Units disposed (in shares) \| shares				18,392,100
Units disposed				$ 16,200
Additional one unit acquired per number of units held (in shares) \| shares	10
Units investments (in shares) \| shares		237,426,088
Units held (in shares) \| shares									237,426,088
Real estate equity securities									$ 35,400
Units, closing price (in dollars per share) \| $ / shares									$ 0.149
Dividend income from real estate equity securities									$ 300	500
Unrealized loss on real estate equity securities									$ 5,200	$ 19,500
SREIT \| SREIT
Schedule of Equity Method Investments [Line Items]
Units disposed (in shares) \| shares			73,720,000
Units disposed			$ 58,900
Disposed of by Sale
Schedule of Equity Method Investments [Line Items]
Number of real estate properties disposed \| property							1	1			2
Disposed of by Sale \| SREIT
Schedule of Equity Method Investments [Line Items]
Number of real estate properties disposed \| property						11