Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2023	May 04, 2023
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q1
Entity Registrant Name	BLACKROCK TCP CAPITAL CORP.
Entity Central Index Key	0001370755
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		57,767,264
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity File Number	814-00899
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
Document Quarterly Report	true
Document Transition Report	false
Entity Incorporation, State or Country Code	DE
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	TCPC
Security Exchange Name	NASDAQ