| Cover | Aug. 26, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Dec. 06, 2022 |
| Entity Registrant Name | KBS REAL ESTATE INVESTMENT TRUST III, INC. |
| Entity Incorporation, State or Country Code | MD |
| Entity File Number | 000-54687 |
| Entity Tax Identification Number | 27-1627696 |
| Entity Address, Address Line One | 800 Newport Center Drive |
| Entity Address, Address Line Two | Suite 700 |
| Entity Address, City or Town | Newport Beach |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 92660 |
| City Area Code | 949 |
| Local Phone Number | 417-6500 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001482430 |
| Amendment Flag | false |
