| Document and Entity Information | Oct. 27, 2022 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Oct. 27, 2022 |
| Entity File Number | 814-00899 |
| Entity Registrant Name | BLACKROCK TCP CAPITAL CORP. |
| Entity Central Index Key | 0001370755 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 56-2594706 |
| Entity Address, Address Line One | 2951 28th Street |
| Entity Address, Address Line Two | Suite 1000 |
| Entity Address, City or Town | Santa Monica |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 90405 |
| City Area Code | 310 |
| Local Phone Number | 566-1000 |
| Title of 12(b) Security | Common stock, $0.001 par value per share |
| Trading Symbol | TCPC |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
