Quarterly report pursuant to Section 13 or 15(d)

Debt - Additional Information (Details)

v3.23.3
Debt - Additional Information (Details)
9 Months Ended 12 Months Ended
Oct. 27, 2020
USD ($)
Sep. 30, 2023
USD ($)
Firm
creditFacility
Dec. 31, 2022
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Firm
creditFacility
Jan. 31, 2023
USD ($)
Sep. 30, 2022
USD ($)
Jun. 23, 2022
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Jun. 22, 2022
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Jan. 20, 2022
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Sep. 16, 2021
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Mar. 04, 2021
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Nov. 04, 2020
USD ($)
Jun. 03, 2020
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Feb. 05, 2020
USD ($)
Jul. 16, 2019
USD ($)
Sep. 24, 2018
USD ($)
Debt Instrument [Line Items]                              
Total Available   $ 2,215,000,000 $ 2,185,000,000                        
Investments, at fair value:   3,261,391,000 2,963,955,000                        
Restricted cash   $ 5,252,000 $ 10,079,000   $ 8,346,000                    
Number of available credit facilities | creditFacility   2 2                        
VIE                              
Debt Instrument [Line Items]                              
Restricted cash   $ 5,252,000 $ 10,079,000                        
Credit Facility                              
Debt Instrument [Line Items]                              
Line of credit interest rate   7.30% 4.51%                        
Debt average amount outstanding   $ 186,600,000 $ 127,700,000                        
MUFG Bank Facility                              
Debt Instrument [Line Items]                              
Maximum borrowing capacity   $ 400,000,000                          
Line of credit facility, description   funded by existing or additional lenders and with the agreement of MUFG Bank and subject to other customary conditions.                          
Line of credit facility, covenant terms   these covenants require the Company to maintain certain financial ratios, including a minimum interest coverage ratio and a minimum tangible net worth with respect to Hercules Funding IV.                          
MUFG Bank Facility | Maximum                              
Debt Instrument [Line Items]                              
Maximum borrowing capacity   $ 600,000,000                          
MUFG Bank Facility | 1-month SOFR                              
Debt Instrument [Line Items]                              
Interest rate plus applicable margin adjustment   2.75%                          
SMBC Facility                              
Debt Instrument [Line Items]                              
Maximum borrowing capacity   $ 225,000,000                          
Line of credit facility, description   Availability under the SMBC Facility will terminate on November 7, 2025, and the outstanding loans under the SMBC Facility will mature on November 9, 2026                          
Line of credit facility, unused capacity, commitment fee percentage   0.375%                          
SMBC Facility | Minimum                              
Debt Instrument [Line Items]                              
Interest rate plus applicable margin adjustment   0.875%                          
SMBC Facility | Maximum                              
Debt Instrument [Line Items]                              
Maximum borrowing capacity   $ 500,000,000                          
Interest rate plus applicable margin adjustment   2.00%                          
SMBC LC Facility                              
Debt Instrument [Line Items]                              
Maximum borrowing capacity   $ 175,000,000   $ 175,000,000                      
SMBC LC Facility | Maximum                              
Debt Instrument [Line Items]                              
Maximum borrowing capacity   400,000,000                          
July 2024 Notes                              
Debt Instrument [Line Items]                              
Total Available   $ 105,000,000 105,000,000                     $ 105,000,000  
Debt instrument, redemption, description   On July 16, 2019, the Company issued $105.0 million in aggregate principal amount of 4.77% interest-bearing unsecured notes due on July 16, 2024 (the “July 2024 Notes”), unless repurchased in accordance with their terms, to qualified institutional investors in a private placement notes offering.                          
Debt instrument, collateral   The July 2024 Notes are general unsecured obligations of the Company that rank pari passu with all outstanding and future unsecured unsubordinated indebtedness issued by the Company.                          
Debt instrument, payment terms, description   Interest on the July 2024 Notes is due semiannually                          
Debt instrument, interest rate   4.77%                          
Debt retired   Jul. 16, 2024                          
February 2025 Notes                              
Debt Instrument [Line Items]                              
Total Available   $ 50,000,000 50,000,000                   $ 50,000,000    
Debt instrument, redemption, description   On February 5, 2020, the Company issued $50.0 million in aggregate principal amount of 4.28% interest-bearing unsecured notes due February 5, 2025 (the “February 2025 Notes”), unless repurchased in accordance with their terms, to qualified institutional investors in a private placement notes offering                          
Debt instrument, collateral   The February 2025 Notes are general unsecured obligations of the Company that rank pari passu with all outstanding and future unsecured unsubordinated indebtedness issued by the Company.                          
Debt instrument, payment terms, description   Interest on the February 2025 Notes is due semiannually                          
Debt instrument, interest rate   4.28%                          
Debt retired   Feb. 05, 2025                          
June 2025 Notes                              
Debt Instrument [Line Items]                              
Total Available   $ 70,000,000 70,000,000                 $ 70,000,000      
Debt instrument, redemption, description   On June 3, 2020, the Company issued $70.0 million in aggregate principal amount of 4.31% interest-bearing unsecured notes due June 3, 2025 (the “June 2025 Notes”), unless repurchased in accordance with their terms, to qualified institutional investors in a private placement notes offering                          
Debt instrument, collateral   The June 2025 Notes are general unsecured obligations of the Company that rank pari passu with all outstanding and future unsecured unsubordinated indebtedness issued by the Company.                          
Debt instrument, payment terms, description   Interest on the June 2025 Notes is due semiannually.                          
Debt instrument, interest rate   4.31%                          
Debt retired   Jun. 03, 2025                          
June 2025 3-Year Notes                              
Debt Instrument [Line Items]                              
Total Available   $ 50,000,000 50,000,000     $ 50,000,000                  
Debt instrument, redemption, description   On June 23, 2022, the Company issued $50.0 million in aggregate principal amount of 6.00% interest-bearing unsecured notes due June 23, 2025 (the “June 2025 3-Year Notes”), unless repurchased in accordance with their terms, to qualified institutional investors in a private placement notes offering                          
Debt instrument, collateral   The June 2025 3-Year Notes are general unsecured obligations of the Company that rank pari passu with all outstanding and future unsecured unsubordinated indebtedness issued by the Company.                          
Debt instrument, payment terms, description   Interest on the June 2025 3-Year Notes is due semiannually.                          
Debt instrument, interest rate   6.00%                          
Debt retired   Jun. 23, 2025                          
March 2026 A Notes                              
Debt Instrument [Line Items]                              
Total Available   $ 50,000,000 50,000,000               $ 50,000,000        
Debt instrument, redemption, description   On November 4, 2020, the Company issued $50.0 million in aggregate principal amount of 4.50% interest-bearing unsecured notes due March 4, 2026 (the “March 2026 A Notes”), unless repurchased in accordance with their terms, to qualified institutional investors in a private placement notes offering                          
Debt instrument, collateral   The March 2026 A Notes are general unsecured obligations of the Company that rank pari passu with all outstanding and future unsecured unsubordinated indebtedness issued by the Company.                          
Debt instrument, payment terms, description   Interest on the March 2026 A Notes is due semiannually                          
Debt instrument, interest rate   4.50%                          
Debt retired   Mar. 04, 2026                          
March 2026 B Notes                              
Debt Instrument [Line Items]                              
Total Available   $ 50,000,000 50,000,000             $ 50,000,000          
Debt instrument, redemption, description   On March 4, 2021, the Company issued $50.0 million in aggregate principal amount of 4.55% interest-bearing unsecured notes due March 4, 2026 (the “March 2026 B Notes”), unless repurchased in accordance with their terms, to qualified institutional investors in a private placement pursuant note offering                          
Debt instrument, collateral   The March 2026 B Notes are general unsecured obligations of the Company that rank pari passu with all outstanding and future unsecured unsubordinated indebtedness issued by the Company.                          
Debt instrument, payment terms, description   Interest on the March 2026 B Notes is due semiannually                          
Debt instrument, interest rate   4.55%                          
Debt retired   Mar. 04, 2026                          
September 2026 Notes                              
Debt Instrument [Line Items]                              
Total Available   $ 325,000,000 325,000,000           $ 325,000,000            
Debt instrument, redemption, description   The Company may redeem some or all of the September 2026 Notes at any time, or from time to time, at the redemption price set forth under the terms of the September 2026 Notes Indenture.                          
Debt instrument, collateral   The September 2026 Notes are general unsecured obligations and rank pari passu, or equally in right of payment, with all outstanding and future unsecured unsubordinated indebtedness issued by the Company.                          
Debt instrument, payment terms, description   Interest on the September 2026 Notes is payable semi-annually in arrears on March 16 and September 16 of each year, commencing on March 16, 2022                          
Debt instrument, interest rate   2.625%                          
Debt retired   Sep. 16, 2026                          
January 2027 Notes                              
Debt Instrument [Line Items]                              
Total Available   $ 350,000,000 350,000,000         $ 350,000,000              
Debt instrument, redemption, description   The Company may redeem some or all of the January 2027 Notes at any time, or from time to time, at the redemption price set forth under the terms of the January 2027 Notes Indenture.                          
Debt instrument, collateral   The January 2027 Notes are general unsecured obligations and rank pari passu, or equally in right of payment, with all outstanding and future unsecured unsubordinated indebtedness issued by the Company.                          
Debt instrument, payment terms, description   Interest on the January 2027 Notes is payable semi-annually in arrears on January 20 and July 20 of each year, commencing on July 20, 2022                          
Debt instrument, interest rate   3.375%                          
Debt retired   Jan. 20, 2027                          
2031 Asset-Backed Notes                              
Debt Instrument [Line Items]                              
Total Available   $ 150,000,000 150,000,000       $ 150,000,000                
Debt instrument, payment terms, description   Interest on the 2031 Asset-Backed Notes will be paid, to the extent of funds available.                          
Debt instrument, interest rate   4.95%                          
Debt retired   Jul. 20, 2031                          
2031 Asset-Backed Notes | VIE                              
Debt Instrument [Line Items]                              
Restricted cash   $ 5,300,000 10,100,000                        
2033 Notes                              
Debt Instrument [Line Items]                              
Total Available   $ 40,000,000 40,000,000                       $ 40,000,000
Debt instrument, redemption, description   The Company may redeem some or all of the 2033 Notes at any time, or from time to time, at the redemption price set forth under the terms of the 2033 Notes indenture after October 30, 2023.                          
Debt instrument, collateral   The 2033 Notes trade on the NYSE under the symbol “HCXY.” The 2033 Notes are general unsecured obligations and rank pari passu, or equally in right of payment, with all outstanding and future unsecured unsubordinated indebtedness issued by the Company.                          
Debt instrument, payment terms, description   Interest on the 2033 Notes is payable quarterly in arrears on January 30, April 30, July 30, and October 30 of each year                          
Debt instrument, interest rate                             6.25%
Debt retired   Oct. 30, 2033                          
HC IV                              
Debt Instrument [Line Items]                              
Debt instrument, license description   HC IV received its license to operate as a SBIC on October 27, 2020. The license has a 10-year term                          
License term 10 years                            
Maximum borrowing capacity $ 175,000,000                            
Regulatory capital commitment amount $ 87,500,000                            
Total Available   $ 175,000,000 $ 175,000,000                        
Investments held by number of companies | Firm   24 21                        
Investments, at fair value:   $ 329,000,000 $ 343,700,000                        
Percentage of total investment portfolio   10.10% 11.60%                        
Tangible assets   $ 333,600,000 $ 348,600,000                        
Percentage of total assets held   10.00% 11.50%