Annual report [Section 13 and 15(d), not S-K Item 405]

Cover Page

v3.25.4
Cover Page - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2025
Feb. 05, 2026
Jun. 30, 2025
Document Information [Line Items]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2025    
Current Fiscal Year End Date --12-31    
Document Transition Report false    
Entity File Number 814-00702    
Entity Registrant Name HERCULES CAPITAL, INC.    
Entity Incorporation, State or Country Code MD    
Entity Tax Identification Number 74-3113410    
Entity Address, Address Line One 1 North B Street    
Entity Address, Address Line Two Suite 2000    
Entity Address, City or Town San Mateo    
Entity Address, State or Province CA    
Entity Address, Postal Zip Code 94401    
City Area Code 650    
Local Phone Number 289-3060    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag true    
Document Financial Statement Error Correction false    
Entity Shell Company false    
Entity Public Float     $ 3,260
Entity Common Stock, Shares Outstanding   183,695,437  
Documents Incorporated By Reference
Portions of the registrant’s Proxy Statement to be filed with the Securities and Exchange Commission pursuant to Regulation 14A in connection with the registrant's 2026 Annual Meeting of Stockholders, which will be filed subsequent to the date hereof, are incorporated by reference into Part III of this Annual Report on Form 10-K. Such proxy statement will be filed with the Securities and Exchange Commission not later than 120 days following the end of the registrant's fiscal year ended December 31, 2025.
    
Entity Central Index Key 0001280784    
Document Fiscal Year Focus 2025    
Document Fiscal Period Focus FY    
Amendment Flag false    
Common Stock Par Value $0.001 Per Share      
Document Information [Line Items]      
Title of 12(b) Security Common Stock, par value $0.001 per share    
Trading Symbol HTGC    
Security Exchange Name NYSE    
6.25% Notes Due 2033      
Document Information [Line Items]      
Title of 12(b) Security 6.25% Notes due 2033    
Trading Symbol HCXY    
Security Exchange Name NYSE