Hercules Capital, Inc. Annual report pursuant to Section 13 and 15(d)

Fair Value of Financial Instruments - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total net change in unrealized appreciation (depreciation)	$ 25,010	$ (85,063)	$ 3,311
2033 Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current price per par value (in dollars per share)	$ 25.25	$ 24.59
2031 Asset-Backed Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current price per par value (in dollars per share)	0.950
Underwriting \| 2033 Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current price per par value (in dollars per share)	$ 25.00