Debt - Additional Information (Details) $ in Thousands |
3 Months Ended | 9 Months Ended | 12 Months Ended | |||||||||||||||||
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Jun. 23, 2022
USD ($)
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Feb. 22, 2022
USD ($)
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Jan. 20, 2022
USD ($)
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Sep. 16, 2021
USD ($)
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Mar. 04, 2021
USD ($)
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Oct. 27, 2020
USD ($)
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Sep. 30, 2022
USD ($)
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Sep. 30, 2021
USD ($)
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Sep. 30, 2022
USD ($)
Firm
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Sep. 30, 2021
USD ($)
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Dec. 31, 2021
USD ($)
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Jun. 22, 2022
USD ($)
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Feb. 01, 2022
USD ($)
shares
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Nov. 04, 2020
USD ($)
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Jun. 03, 2020
USD ($)
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Feb. 05, 2020
USD ($)
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Jul. 16, 2019
USD ($)
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Sep. 24, 2018
USD ($)
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Oct. 23, 2017
USD ($)
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Jan. 25, 2017
USD ($)
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| Debt Instrument [Line Items] | ||||||||||||||||||||
| Debt Instrument Face Amount | $ 2,185,000 | $ 2,185,000 | $ 1,745,000 | $ 150,000 | ||||||||||||||||
| Investment Owned At Fair Value | $ 2,825,738 | $ 2,825,738 | 2,434,522 | |||||||||||||||||
| Debt instrument, interest rate | 4.625% | 4.625% | ||||||||||||||||||
| Debt Instrument Maturity Date | Oct. 23, 2022 | |||||||||||||||||||
| Debt Instrument, redemption, description | On October 23, 2017, the Company issued $150.0 million in aggregate principal amount of 4.625% interest-bearing unsecured notes that mature on October 23, 2022 (the “2022 Notes”), unless repurchased in accordance with their terms | |||||||||||||||||||
| Repayment of debt | $ 150,000 | |||||||||||||||||||
| Interest payable | 2,300 | |||||||||||||||||||
| Gain (loss) on extinguishment of debt | $ 0 | $ (1,702) | $ (3,686) | $ (1,702) | ||||||||||||||||
| Restricted cash (amounts related to a VIE $8,346 and $0, respectively) | 8,346 | $ 13,509 | $ 8,346 | $ 13,509 | 3,150 | |||||||||||||||
| Line of credit facility, termination date | Nov. 09, 2026 | |||||||||||||||||||
| 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. | |||||||||||||||||||
| Variable Interest Entity Primary Beneficiary [Member] | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Restricted cash (amounts related to a VIE $8,346 and $0, respectively) | 8,346 | $ 8,346 | 0 | |||||||||||||||||
| MUFG Bank Facility | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Line of Credit Facility, Covenant Terms | these covenants require the Company to maintain certain financial ratios, including a minimum interest coverage ratio with respect to Hercules Funding IV and a minimum tangible net worth in an amount that is in excess of $723.0 million. | |||||||||||||||||||
| Line of credit facility, termination date | Feb. 22, 2024 | |||||||||||||||||||
| Minimum tangible net worth amount | 723,000 | $ 723,000 | ||||||||||||||||||
| Maximum borrowing capacity | 545,000 | $ 545,000 | ||||||||||||||||||
| Line of Credit Facility, Description | The MUFG Bank Facility contains an accordion feature, in which the Company can increase the credit line up to an aggregate of $600.0 million, funded by existing or additional lenders and with the agreement of MUFG Bank and subject to other customary conditions. | |||||||||||||||||||
| MUFG Bank Facility | Maximum | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Maximum borrowing capacity | 600,000 | $ 600,000 | ||||||||||||||||||
| MUFG Bank Facility | One-month interest period | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Interest rate plus applicable margin adjustment | 2.60% | |||||||||||||||||||
| MUFG Bank Facility | Three-month interest period | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Interest rate plus applicable margin adjustment | 2.65% | |||||||||||||||||||
| MUFG Bank Facility | Lender [Member] | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Maximum borrowing capacity | 400,000 | |||||||||||||||||||
| S M B C Facility [Member] | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Line of credit facility, termination date | Nov. 07, 2025 | |||||||||||||||||||
| Maximum borrowing capacity | 225,000 | $ 225,000 | 100,000 | |||||||||||||||||
| Line of Credit Facility, Description | the SMBC Facility provides for the issuance of letters of credit on the account of the Company or its designee in U.S. dollars and certain agreed upon foreign currencies in an aggregate face amount not to exceed $15.0 million. | |||||||||||||||||||
| Line of credit facility, unused capacity, commitment fee percentage | 0.375% | |||||||||||||||||||
| S M B C Facility [Member] | Minimum | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Interest rate plus applicable margin adjustment | 0.875% | |||||||||||||||||||
| S M B C Facility [Member] | Maximum | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Interest rate plus applicable margin adjustment | 2.00% | |||||||||||||||||||
| Credit Facility [Member] | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Debt average amount outstanding | $ 115,600 | $ 28,800 | ||||||||||||||||||
| Line of credit interest rate | 3.70% | 2.54% | ||||||||||||||||||
| Debt Issuance Cost | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Gain (loss) on extinguishment of debt | (300) | |||||||||||||||||||
| Prepayment Fees | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Gain (loss) on extinguishment of debt | $ (3,300) | |||||||||||||||||||
| Foreign Currency Borrowing Member | S M B C Facility [Member] | Maximum | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Maximum borrowing capacity | 15,000 | $ 15,000 | ||||||||||||||||||
| 2022 Convertible Notes | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Debt Instrument Face Amount | $ 0 | $ 0 | $ 230,000 | $ 230,000 | ||||||||||||||||
| Debt instrument, interest rate | 4.375% | 4.375% | ||||||||||||||||||
| Debt Instrument Maturity Date | Feb. 01, 2022 | |||||||||||||||||||
| Debt Instrument, redemption, description | On January 25, 2017, the Company issued $230.0 million in aggregate principal amount of 4.375% interest-bearing unsecured notes due on February 1, 2022 (the “2022 Convertible Notes”), unless previously converted or caused to repurchase the notes in accordance with their terms by the holders of the 2022 Convertible Notes | |||||||||||||||||||
| Repayment of debt | $ 230,000 | |||||||||||||||||||
| Interest payable | $ 5,000 | |||||||||||||||||||
| Debt instrument, payment terms, description | Interest on the 2022 Convertible Notes is due semiannually in arrears on February 1 and August 1 of each year | |||||||||||||||||||
| Convertible Debt Redemption Shares Issued on Redemption | shares | 981,169 | |||||||||||||||||||
| 2022 Convertible Notes | Additional Face Amount [Member] | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Debt Instrument Face Amount | $ 30,000 | |||||||||||||||||||
| July 2024 Notes | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Debt Instrument Face Amount | $ 105,000 | |||||||||||||||||||
| Debt instrument, interest rate | 4.77% | 4.77% | ||||||||||||||||||
| Debt Instrument Maturity Date | Jul. 16, 2024 | |||||||||||||||||||
| 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, payment terms, description | Interest on the July 2024 Notes is due semiannually | |||||||||||||||||||
| 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. | |||||||||||||||||||
| February 2025 Notes | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Debt Instrument Face Amount | $ 50,000 | |||||||||||||||||||
| Debt instrument, interest rate | 4.28% | 4.28% | ||||||||||||||||||
| Debt Instrument Maturity Date | Feb. 05, 2025 | |||||||||||||||||||
| Debt Instrument, redemption, description | On February 5, 2020, the Company issued $50.0 million in aggregate principal amount of 4.28% 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, payment terms, description | Interest on the February 2025 Notes is due semiannually | |||||||||||||||||||
| 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. | |||||||||||||||||||
| June 2025 Notes | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Debt Instrument Face Amount | $ 70,000 | |||||||||||||||||||
| Debt instrument, interest rate | 4.31% | 4.31% | ||||||||||||||||||
| Debt Instrument Maturity Date | Jun. 03, 2025 | |||||||||||||||||||
| Debt Instrument, redemption, description | On June 3, 2020, the Company issued $70.0 million in aggregate principal amount of 4.31% 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, payment terms, description | Interest on the June 2025 Notes is due semiannually. | |||||||||||||||||||
| 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. | |||||||||||||||||||
| June 2025 3-Year Notes | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Debt Instrument Face Amount | $ 50,000 | |||||||||||||||||||
| Debt instrument, interest rate | 6.00% | 6.00% | ||||||||||||||||||
| Debt Instrument Maturity Date | Jun. 23, 2025 | |||||||||||||||||||
| Debt Instrument, redemption, description | On June 23, 2022, the Company issued $50.0 million in aggregate principal amount of 6.00% 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, payment terms, description | Interest on the June 2025 3-Year Notes is due semiannually. | |||||||||||||||||||
| 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. | |||||||||||||||||||
| March 2026 A Notes | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Debt Instrument Face Amount | $ 50,000 | |||||||||||||||||||
| Debt instrument, interest rate | 4.50% | 4.50% | ||||||||||||||||||
| Debt Instrument Maturity Date | Mar. 04, 2026 | |||||||||||||||||||
| Debt Instrument, redemption, description | On November 4, 2020, the Company issued $50.0 million in aggregate principal amount of 4.5% 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, payment terms, description | Interest on the March 2026 A Notes is due semiannually | |||||||||||||||||||
| 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. | |||||||||||||||||||
| March 2026 B Notes | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Debt Instrument Face Amount | $ 50,000 | |||||||||||||||||||
| Debt instrument, interest rate | 4.55% | 4.55% | ||||||||||||||||||
| Debt Instrument Maturity Date | Mar. 04, 2026 | |||||||||||||||||||
| 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, payment terms, description | Interest on the March 2026 B Notes is due semiannually | |||||||||||||||||||
| Net proceeds from sale of Notes | 49,500 | |||||||||||||||||||
| Aggregate Debt Issuance Cost | $ 500 | |||||||||||||||||||
| 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. | |||||||||||||||||||
| September 2026 Notes | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Debt Instrument Face Amount | $ 325,000 | |||||||||||||||||||
| Debt instrument, interest rate | 2.625% | 2.625% | ||||||||||||||||||
| Debt Instrument Maturity Date | Sep. 16, 2026 | |||||||||||||||||||
| 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, 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 | |||||||||||||||||||
| Net proceeds from sale of Notes | 320,100 | |||||||||||||||||||
| Aggregate Debt Issuance Cost | 4,100 | |||||||||||||||||||
| Aggregate Discount On Issuance | $ 800 | |||||||||||||||||||
| 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. | |||||||||||||||||||
| January 2027 Notes | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Debt Instrument Face Amount | $ 350,000 | |||||||||||||||||||
| Debt instrument, interest rate | 3.375% | 3.375% | ||||||||||||||||||
| Debt Instrument 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 January 2027 Notes Indenture. | |||||||||||||||||||
| 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 | |||||||||||||||||||
| Net proceeds from sale of Notes | 343,400 | |||||||||||||||||||
| Aggregate Debt Issuance Cost | 4,100 | |||||||||||||||||||
| Aggregate Discount On Issuance | $ 2,500 | |||||||||||||||||||
| 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. | |||||||||||||||||||
| 2031 Asset-Backed Notes | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Debt Instrument Face Amount | $ 150,000 | |||||||||||||||||||
| Debt instrument, interest rate | 4.95% | 4.95% | ||||||||||||||||||
| Debt Instrument 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. | |||||||||||||||||||
| 2031 Asset-Backed Notes | Variable Interest Entity Primary Beneficiary [Member] | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Restricted cash (amounts related to a VIE $8,346 and $0, respectively) | $ 8,300 | $ 8,300 | $ 0 | |||||||||||||||||
| 2033 Notes | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Debt Instrument Face Amount | $ 40,000 | |||||||||||||||||||
| Debt instrument, interest rate | 6.25% | 6.25% | ||||||||||||||||||
| Debt Instrument 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 2033 Notes 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. | |||||||||||||||||||
| HC IV | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| License term | 10 years | |||||||||||||||||||
| 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. | |||||||||||||||||||
| Regulatory capital commitment amount | $ 87,500 | |||||||||||||||||||
| Debt Instrument Face Amount | $ 175,000 | $ 175,000 | ||||||||||||||||||
| Investments held by number of companies | Firm | 18 | |||||||||||||||||||
| Investment Owned At Fair Value | $ 277,100 | $ 277,100 | ||||||||||||||||||
| Percentage of total investment portfolio | 9.80% | 9.80% | ||||||||||||||||||
| Tangible Assets | $ 287,600 | $ 287,600 | ||||||||||||||||||
| Percentage of total assets held | 9.80% | 9.80% | ||||||||||||||||||
| Maximum borrowing capacity | $ 175,000 | |||||||||||||||||||
| HC IV | SBA Commitment Fee [Member] | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Debt issuance cost | $ 1,750 | $ 1,750 | ||||||||||||||||||
| HC IV | SBA Facility Fee [Member] | ||||||||||||||||||||
| Debt Instrument [Line Items] | ||||||||||||||||||||
| Debt issuance cost | $ 4,200 | $ 4,200 | ||||||||||||||||||