| Document and Entity Information | Mar. 18, 2024 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Mar. 18, 2024 |
| Entity File Number | 814-00712 |
| Entity Registrant Name | BLACKROCK CAPITAL INVESTMENT CORPORATION |
| Entity Central Index Key | 0001326003 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 20-2725151 |
| Entity Address, Address Line One | 50 Hudson Yards |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10001 |
| City Area Code | 212 |
| Local Phone Number | 810-5800 |
| Title of 12(b) Security | Common Stock, $0.001 par value |
| Trading Symbol | BKCC |
| 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 |
