Main Street Capital Corporation Quarterly report pursuant to Section 13 or 15(d)

DEBT - Schedule of Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Debt Instrument [Line Items]
Total Interest Expense	$ 26,414	$ 21,234	$ 78,165	$ 55,216
July 2026 Notes \| Unsecured Notes
Debt Instrument [Line Items]
Total Interest Expense	3,882	3,882	11,645	11,645
May 2024 Notes \| Unsecured Notes
Debt Instrument [Line Items]
Total Interest Expense	5,714	5,714	17,141	17,141
SBIC Debentures \| Unsecured Notes
Debt Instrument [Line Items]
Total Interest Expense	2,965	2,855	8,435	8,482
December 2025 Notes \| Unsecured Notes
Debt Instrument [Line Items]
Total Interest Expense	3,031	0	8,673	0
December 2022 Notes \| Unsecured Notes
Debt Instrument [Line Items]
Total Interest Expense	0	2,233	0	6,699
Credit Facility \| Corporate Facility \| Line of Credit
Debt Instrument [Line Items]
Total Interest Expense	7,157	6,551	21,666	11,249
Credit Facility \| SPV Facility \| Line of Credit
Debt Instrument [Line Items]
Total Interest Expense	$ 3,665	$ 0	$ 10,605	$ 0