Main Street Capital Corporation Quarterly report [Sections 13 or 15(d)]

DEBT - Schedule of Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Debt Instrument [Line Items]
Total Interest Expense	$ 32,472	$ 33,474	$ 96,159	$ 89,411
July 2026 Notes \| Unsecured Notes
Debt Instrument [Line Items]
Total Interest Expense	3,882	3,882	11,645	11,645
June 2027 Notes \| Unsecured Notes
Debt Instrument [Line Items]
Total Interest Expense	6,572	5,316	19,715	6,790
August 2028 Notes \| Unsecured Notes
Debt Instrument [Line Items]
Total Interest Expense	2,452	0	2,452	0
March 2029 Notes \| Unsecured Notes
Debt Instrument [Line Items]
Total Interest Expense	6,261	6,261	18,783	18,008
SBIC debentures \| Unsecured Notes
Debt Instrument [Line Items]
Total Interest Expense	3,166	2,492	9,452	7,472
December 2025 Notes \| Unsecured Notes
Debt Instrument [Line Items]
Total Interest Expense	2,999	3,031	9,060	9,092
May 2024 Notes \| Unsecured Notes
Debt Instrument [Line Items]
Total Interest Expense	0	0	0	7,618
Credit Facility \| Corporate Facility \| Line of Credit
Debt Instrument [Line Items]
Total Interest Expense	4,107	8,551	14,431	20,071
Credit Facility \| SPV Facility \| Line of Credit
Debt Instrument [Line Items]
Total Interest Expense	$ 3,033	$ 3,941	$ 10,621	$ 8,715