Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2022	Aug. 03, 2022
Cover [Abstract]
Document Type	10-Q/A
Amendment Flag	true
Document Period End Date	Jun. 30, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--12-31
Document Quarterly Report	true
Document Transition Report	false
Securities Act File Number	814-00899
Trading Symbol	TCPC
Entity Registrant Name	BLACKROCK TCP CAPITAL CORP.
Entity Central Index Key	0001370755
Entity Filer Category	Large Accelerated Filer
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
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, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		57,767,264
Amendment Description	EXPLANATORY NOTE The registrant’s Form 10-Q filed with the SEC on August 3, 2022 did not include inline XBRL tagging. The sole purpose of this Amendment No. 1 to the registrant’s Form 10-Q for the quarterly period ended June 30, 2022 is to add inline XBRL tagging to the Form 10-Q in accordance with Rule 405 of Regulation S-T.  No changes have been made to the registrant’s Form 10-Q. This Amendment No. 1 does not reflect any subsequent events occurring after the original filing date of the Form 10-Q or modify or update in any way disclosures made in the original filing.