Debt - Narrative (Details) |
3 Months Ended | 9 Months Ended | 12 Months Ended | ||||||||||||||||||||||||
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Sep. 16, 2026
USD ($)
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Mar. 04, 2026
USD ($)
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Jun. 23, 2025
USD ($)
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Jun. 03, 2025
USD ($)
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Mar. 10, 2025
USD ($)
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Feb. 05, 2025
USD ($)
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Jul. 09, 2024 |
Oct. 27, 2020
USD ($)
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Sep. 30, 2026
USD ($)
creditFacility
$ / shares
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Sep. 30, 2025
USD ($)
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Sep. 30, 2026
USD ($)
creditFacility
$ / shares
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Sep. 30, 2025
USD ($)
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Dec. 31, 2025
USD ($)
creditFacility
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Jul. 24, 2026
USD ($)
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Feb. 10, 2026
USD ($)
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Jun. 16, 2025
USD ($)
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Jun. 10, 2025
USD ($)
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Jun. 09, 2025
USD ($)
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Jun. 23, 2022
USD ($)
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Jun. 22, 2022
USD ($)
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Jan. 20, 2022
USD ($)
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Sep. 16, 2021
USD ($)
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Mar. 04, 2021
USD ($)
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Nov. 04, 2020
USD ($)
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Jun. 03, 2020
USD ($)
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Feb. 05, 2020
USD ($)
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Sep. 24, 2018
USD ($)
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|
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Outstanding principal balances | $ 3,042,160,000 | $ 3,042,160,000 | $ 2,782,136,000 | ||||||||||||||||||||||||
| Repayments of debt | 1,598,568,000 | $ 1,285,836,000 | |||||||||||||||||||||||||
| Restricted cash | 2,225,000 | $ 21,087,000 | 2,225,000 | 21,087,000 | $ 2,467,000 | ||||||||||||||||||||||
| Loss on extinguishment of debt | $ 0 | 84,000 | $ 2,000 | 120,000 | |||||||||||||||||||||||
| Number of available credit facilities | creditFacility | 2 | 2 | 2 | ||||||||||||||||||||||||
| Credit Facility | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Line of credit interest rate | 5.74% | 6.14% | |||||||||||||||||||||||||
| Debt average amount outstanding | $ 324,600,000 | $ 328,300,000 | |||||||||||||||||||||||||
| MUFG Bank Facility | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Line of credit facility, termination date | Jan. 13, 2026 | ||||||||||||||||||||||||||
| SMBC LC Facility | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Maximum borrowing capacity | $ 300,000,000.0 | $ 300,000,000.0 | |||||||||||||||||||||||||
| Line of credit facility, unused capacity, commitment fee percentage | 0.375% | ||||||||||||||||||||||||||
| SMBC LC Facility | Term Loan | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Outstanding principal balances | 25,000,000.0 | $ 25,000,000.0 | |||||||||||||||||||||||||
| Interest rate plus applicable margin adjustment | 2.00% | ||||||||||||||||||||||||||
| SMBC LC Facility | Maximum | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Interest rate plus applicable margin adjustment | 2.00% | ||||||||||||||||||||||||||
| SMBC LC Facility | Minimum | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Interest rate plus applicable margin adjustment | 1.00% | ||||||||||||||||||||||||||
| VIE | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Restricted cash | 2,225,000 | $ 2,225,000 | 2,467,000 | ||||||||||||||||||||||||
| SBA Debentures | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Maximum borrowing capacity | 425,000,000.0 | 425,000,000.0 | 350,000,000.0 | ||||||||||||||||||||||||
| Outstanding principal balances | 425,000,000 | $ 425,000,000 | 350,000,000 | ||||||||||||||||||||||||
| SBA Debentures | HC IV | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Debt instrument, license description | HC IV and SBIC V each received their licenses to operate as an SBIC on October 27, 2020 and July 9, 2024, respectively, and each license has a 10-year term. | ||||||||||||||||||||||||||
| License term | 10 years | ||||||||||||||||||||||||||
| Maximum borrowing capacity | $ 175,000,000.0 | 175,000,000.0 | $ 175,000,000.0 | 175,000,000.0 | |||||||||||||||||||||||
| Debenture capacity issued | 175,000,000.0 | $ 175,000,000.0 | |||||||||||||||||||||||||
| SBA Debentures | SBIC V | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Debt instrument, license description | HC IV and SBIC V each received their licenses to operate as an SBIC on October 27, 2020 and July 9, 2024, respectively, and each license has a 10-year term. | ||||||||||||||||||||||||||
| License term | 10 years | ||||||||||||||||||||||||||
| Maximum borrowing capacity | 250,000,000.0 | $ 250,000,000.0 | 175,000,000.0 | ||||||||||||||||||||||||
| Debenture capacity issued | 175,000,000.0 | 175,000,000.0 | |||||||||||||||||||||||||
| Accordion feature, increase limit | 75,000,000.0 | $ 75,000,000.0 | |||||||||||||||||||||||||
| February 2025 Notes | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Outstanding principal balances | $ 50,000,000.0 | ||||||||||||||||||||||||||
| Debt instrument, interest rate | 4.28% | ||||||||||||||||||||||||||
| Maturity date | Feb. 05, 2025 | ||||||||||||||||||||||||||
| Debt instrument, redemption, description | On February 5, 2020, the Company issued $50.0 million in aggregate principal amount of 4.280% 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, payment terms, description | Interest on the February 2025 Notes was due semiannually | ||||||||||||||||||||||||||
| Debt instrument, collateral | The February 2025 Notes were the general unsecured obligations of the Company that ranked pari passu with all outstanding and future unsecured unsubordinated indebtedness issued by the Company. | ||||||||||||||||||||||||||
| Repayments of debt | $ 50,000,000.0 | ||||||||||||||||||||||||||
| Repayment of accrued interest | 1,100,000 | ||||||||||||||||||||||||||
| June 2025 Notes | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Outstanding principal balances | $ 70,000,000.0 | ||||||||||||||||||||||||||
| Debt instrument, interest rate | 4.31% | ||||||||||||||||||||||||||
| Maturity date | Jun. 03, 2025 | ||||||||||||||||||||||||||
| Debt instrument, redemption, description | On June 3, 2020, the Company issued $70.0 million in aggregate principal amount of 4.310% 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, payment terms, description | Interest on the June 2025 Notes was due semiannually. | ||||||||||||||||||||||||||
| Debt instrument, collateral | The June 2025 Notes were the general unsecured obligations of the Company that ranked pari passu with all outstanding and future unsecured unsubordinated indebtedness issued by the Company. | ||||||||||||||||||||||||||
| Repayments of debt | $ 70,000,000.0 | ||||||||||||||||||||||||||
| Repayment of accrued interest | $ 1,500,000 | ||||||||||||||||||||||||||
| June 2025 3-Year Notes | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Outstanding principal balances | $ 50,000,000.0 | ||||||||||||||||||||||||||
| Debt instrument, interest rate | 6.00% | ||||||||||||||||||||||||||
| Maturity date | Jun. 23, 2025 | ||||||||||||||||||||||||||
| Debt instrument, redemption, description | On June 23, 2022, the Company issued $50.0 million in aggregate principal amount of 6.000% 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, payment terms, description | Interest on the June 2025 3-Year Notes was due semiannually. | ||||||||||||||||||||||||||
| Debt instrument, collateral | The June 2025 3-Year Notes were the general unsecured obligations of the Company that ranked pari passu with all outstanding and future unsecured unsubordinated indebtedness issued by the Company. | ||||||||||||||||||||||||||
| Repayments of debt | $ 50,000,000.0 | ||||||||||||||||||||||||||
| Repayment of accrued interest | $ 1,500,000 | ||||||||||||||||||||||||||
| March 2026 A Notes | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Outstanding principal balances | 0 | $ 0 | 50,000,000 | $ 50,000,000.0 | |||||||||||||||||||||||
| Debt instrument, interest rate | 4.50% | ||||||||||||||||||||||||||
| Maturity date | Mar. 04, 2026 | ||||||||||||||||||||||||||
| Debt instrument, payment terms, description | Interest on the March 2026 A Notes was due semiannually | ||||||||||||||||||||||||||
| Debt instrument, collateral | The March 2026 A Notes were the general unsecured obligations of the Company that ranked pari passu with all outstanding and future unsecured unsubordinated indebtedness issued by the Company. | ||||||||||||||||||||||||||
| Repayments of debt | $ 50,000,000.0 | ||||||||||||||||||||||||||
| Repayment of accrued interest | 1,100,000 | ||||||||||||||||||||||||||
| March 2026 B Notes | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Outstanding principal balances | 0 | $ 0 | 50,000,000 | $ 50,000,000.0 | |||||||||||||||||||||||
| Debt instrument, interest rate | 4.55% | ||||||||||||||||||||||||||
| Maturity date | Mar. 04, 2026 | ||||||||||||||||||||||||||
| Debt instrument, payment terms, description | Interest on the March 2026 B Notes was due semiannually | ||||||||||||||||||||||||||
| Debt instrument, collateral | The March 2026 B Notes were the general unsecured obligations of the Company that ranked pari passu with all outstanding and future unsecured unsubordinated indebtedness issued by the Company. | ||||||||||||||||||||||||||
| Repayments of debt | 50,000,000.0 | ||||||||||||||||||||||||||
| Repayment of accrued interest | $ 1,100,000 | ||||||||||||||||||||||||||
| September 2026 Notes | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Outstanding principal balances | 0 | $ 0 | 325,000,000 | $ 325,000,000.0 | |||||||||||||||||||||||
| Debt instrument, interest rate | 2.625% | ||||||||||||||||||||||||||
| Maturity date | Sep. 16, 2026 | ||||||||||||||||||||||||||
| Debt instrument, payment terms, description | Interest on the September 2026 Notes was payable semiannually in arrears on March 16 and September 16 of each year. | ||||||||||||||||||||||||||
| Debt instrument, collateral | The September 2026 Notes were general unsecured obligations and ranked pari passu, or equally in right of payment, with all outstanding and future unsecured unsubordinated indebtedness issued by the Company. | ||||||||||||||||||||||||||
| Repayments of debt | $ 325,000,000.0 | ||||||||||||||||||||||||||
| Repayment of accrued interest | $ 4,300,000 | ||||||||||||||||||||||||||
| January 2027 Notes | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Outstanding principal balances | 350,000,000 | $ 350,000,000 | 350,000,000 | $ 350,000,000.0 | |||||||||||||||||||||||
| Debt instrument, interest rate | 3.375% | ||||||||||||||||||||||||||
| Maturity date | Jan. 20, 2027 | ||||||||||||||||||||||||||
| 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 Eighth Supplemental Indenture. | ||||||||||||||||||||||||||
| Debt instrument, payment terms, description | Interest on the January 2027 Notes is payable semiannually in arrears on January 20 and July 20 of each year. | ||||||||||||||||||||||||||
| 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. | ||||||||||||||||||||||||||
| 2028 Convertible Notes | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Outstanding principal balances | $ 287,500,000 | $ 287,500,000 | $ 287,500,000 | 287,500,000 | |||||||||||||||||||||||
| Debt instrument, interest rate | 4.75% | ||||||||||||||||||||||||||
| Maturity date | Sep. 01, 2028 | ||||||||||||||||||||||||||
| Debt instrument, redemption, description | On March 10, 2025, the Company issued $287.5 million in aggregate principal amount of 4.750% interest-bearing convertible unsecured notes due on September 1, 2028 (the “2028 Convertible Notes”), unless previously converted or caused to repurchase the notes in accordance with their terms by the holders of the 2028 Convertible Notes. The Company may not redeem the 2028 Convertible Notes at its option prior to maturity. | ||||||||||||||||||||||||||
| Debt instrument, payment terms, description | Interest on the 2028 Convertible Notes is due semiannually. | ||||||||||||||||||||||||||
| Debt instrument, collateral | The 2028 Convertible Notes are unsecured obligations of the Company and rank pari passu, or equally in right of payment, with all outstanding and future unsecured unsubordinated indebtedness issued by the Company. | ||||||||||||||||||||||||||
| Initial conversion ratio (in dollars per share) | 0.0465631 | ||||||||||||||||||||||||||
| Conversion price (in dollars per share) | $ / shares | $ 21.48 | $ 21.48 | |||||||||||||||||||||||||
| February 2029 Notes | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Outstanding principal balances | $ 300,000,000 | $ 300,000,000 | 0 | $ 300,000,000.0 | |||||||||||||||||||||||
| Debt instrument, interest rate | 5.35% | ||||||||||||||||||||||||||
| Maturity date | Feb. 10, 2029 | ||||||||||||||||||||||||||
| Debt instrument, redemption, description | The Company may redeem some or all of the February 2029 Notes at any time, or from time to time, at the redemption price set forth under the terms of the Tenth Supplemental Indenture. | ||||||||||||||||||||||||||
| Debt instrument, payment terms, description | Interest on the February 2029 Notes is payable semiannually in arrears on February 10 and August 10 of each year, commencing August 10, 2026. | ||||||||||||||||||||||||||
| Debt instrument, collateral | The February 2029 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. | ||||||||||||||||||||||||||
| June 2030 Notes | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Outstanding principal balances | 350,000,000 | $ 350,000,000 | 350,000,000 | $ 350,000,000.0 | |||||||||||||||||||||||
| Debt instrument, interest rate | 6.00% | ||||||||||||||||||||||||||
| Maturity date | Jun. 16, 2030 | ||||||||||||||||||||||||||
| Debt instrument, redemption, description | The Company may redeem some or all of the June 2030 Notes at any time, or from time to time, at the redemption price set forth under the terms of the Ninth Supplemental Indenture. | ||||||||||||||||||||||||||
| Debt instrument, payment terms, description | Interest on the June 2030 Notes is payable semiannually in arrears on June 16 and December 16 of each year, commencing December 16, 2025. | ||||||||||||||||||||||||||
| Debt instrument, collateral | The June 2030 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. | ||||||||||||||||||||||||||
| 2031 Asset-Backed Notes | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Outstanding principal balances | 49,660,000 | $ 49,660,000 | 64,636,000 | $ 150,000,000.0 | |||||||||||||||||||||||
| Debt instrument, interest rate | 4.95% | ||||||||||||||||||||||||||
| Maturity date | Jul. 20, 2031 | ||||||||||||||||||||||||||
| Debt instrument, payment terms, description | Interest on the 2031 Asset-Backed Notes will be paid, to the extent of funds available. | ||||||||||||||||||||||||||
| Repayments of debt | 1,100,000 | 22,900,000 | $ 15,000,000.0 | 30,800,000 | |||||||||||||||||||||||
| Loss on extinguishment of debt | 0 | $ 84,000 | 2,000 | $ 120,000 | |||||||||||||||||||||||
| 2031 Asset-Backed Notes | VIE | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Restricted cash | 2,200,000 | 2,200,000 | 2,500,000 | ||||||||||||||||||||||||
| July 2031 Notes | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Outstanding principal balances | 325,000,000 | $ 325,000,000 | 0 | $ 325,000,000.0 | |||||||||||||||||||||||
| Debt instrument, interest rate | 6.30% | ||||||||||||||||||||||||||
| Maturity date | Jul. 24, 2031 | ||||||||||||||||||||||||||
| Debt instrument, redemption, description | The Company may redeem some or all of the July 2031 Notes at any time, or from time to time, at the redemption price set forth under the terms of the Eleventh Supplemental Indenture. | ||||||||||||||||||||||||||
| Debt instrument, payment terms, description | Interest on the July 2031 Notes is payable semiannually in arrears on January 24 and July 24 of each year, commencing January 24, 2027. | ||||||||||||||||||||||||||
| Debt instrument, collateral | The July 2031 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. | ||||||||||||||||||||||||||
| 2033 Notes | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Outstanding principal balances | 40,000,000 | $ 40,000,000 | 40,000,000 | $ 40,000,000.0 | |||||||||||||||||||||||
| Debt instrument, interest rate | 6.25% | ||||||||||||||||||||||||||
| Maturity date | Oct. 30, 2033 | ||||||||||||||||||||||||||
| 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 Sixth Supplemental Indenture after October 30, 2023. | ||||||||||||||||||||||||||
| 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, 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. | ||||||||||||||||||||||||||
| MUFG Bank Facility | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Outstanding principal balances | 440,000,000 | $ 440,000,000 | 440,000,000 | ||||||||||||||||||||||||
| MUFG Bank Facility | Line of credit | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Maximum borrowing capacity | $ 440,000,000.0 | $ 400,000,000.0 | |||||||||||||||||||||||||
| Line of credit facility, description | funded by existing or additional lenders and with the agreement of MUFG Bank and subject to other customary conditions. | ||||||||||||||||||||||||||
| Interest rate plus applicable margin adjustment | 2.75% | ||||||||||||||||||||||||||
| 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 | Line of credit | Maximum | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Accordion feature, increase limit | 600,000,000.0 | $ 600,000,000.0 | |||||||||||||||||||||||||
| Additional basis spread on variable rate | 2.75% | ||||||||||||||||||||||||||
| MUFG Bank Facility | Line of credit | Minimum | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Additional basis spread on variable rate | 2.50% | ||||||||||||||||||||||||||
| SMBC Facility | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Outstanding principal balances | 475,000,000 | $ 475,000,000 | 475,000,000 | ||||||||||||||||||||||||
| SMBC Facility | Term Loan | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Outstanding principal balances | 25,000,000.0 | 25,000,000.0 | 25,000,000.0 | ||||||||||||||||||||||||
| SMBC Facility | SMBC LC Facility | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Maximum borrowing capacity | 175,000,000.0 | 175,000,000.0 | $ 175,000,000.0 | $ 175,000,000.0 | |||||||||||||||||||||||
| Accordion feature, increase limit | $ 400,000,000.0 | ||||||||||||||||||||||||||
| Line of credit facility, description | Availability under the revolving SMBC Facility will terminate on November 24, 2028, and the outstanding loans under the SMBC Facility will mature on November 26, 2029 | ||||||||||||||||||||||||||
| Line of credit facility, termination date | Feb. 05, 2028 | ||||||||||||||||||||||||||
| SMBC Facility | SMBC LC Facility | Maximum | |||||||||||||||||||||||||||
| Debt Instrument [Line Items] | |||||||||||||||||||||||||||
| Accordion feature, increase limit | $ 500,000,000.0 | $ 500,000,000.0 | |||||||||||||||||||||||||