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

Quarterly report pursuant to Section 13 or 15(d)

RELATED PARTY TRANSACTIONS (Details)

RELATED PARTY TRANSACTIONS (Details) - Related Party - USD ($)		1 Months Ended					9 Months Ended
	Dec. 29, 2021	Sep. 30, 2023	Aug. 31, 2023	Mar. 31, 2022	Feb. 28, 2022	Dec. 31, 2020	Sep. 30, 2023	May 31, 2023	May 31, 2022
External Investment Manager
Related Party Transaction [Line Items]
Receivable		$ 9,400,000					$ 9,400,000
MSC Income
Related Party Transaction [Line Items]
Shares acquired (in shares)		814,379	348,542				814,379	255,755	94,697
Operating Expenses and Amount Due From Tax Sharing Agreement \| External Investment Manager
Related Party Transaction [Line Items]
Receivable		$ 7,200,000					$ 7,200,000
Dividends Declared But Not Yet Paid \| External Investment Manager
Related Party Transaction [Line Items]
Receivable		$ 2,200,000					$ 2,200,000
Dutch Auction \| MSC Income
Related Party Transaction [Line Items]
Shares acquired (in shares)		115,385					115,385
Sale of stock, price per share (in dollars per share)		$ 6.50					$ 6.50
Sale of stock, authorized consideration on transaction			$ 3,500,000
Investment Management Agreement \| Private Loan Fund
Related Party Transaction [Line Items]
Amounts of transaction					$ 15,000,000	$ 10,000,000
Funded commitments							$ 14,300,000
Unfunded commitments		$ 700,000					700,000
Investment Management Agreement \| Private Loan Fund II
Related Party Transaction [Line Items]
Amounts of transaction		15,000,000
Funded commitments							1,200,000
Unfunded commitments		$ 6,500,000					$ 6,500,000
Percentage of total commitments		20.00%					20.00%
Unsecured Revolving Promissory Note \| Private Loan Fund
Related Party Transaction [Line Items]
Amounts of transaction	$ 85,000,000
Interest rate (as a percent)	5.00%
Secured Revolving Promissory Note \| Private Loan Fund
Related Party Transaction [Line Items]
Amounts of transaction				$ 10,000,000
Interest rate (as a percent)				5.00%
Unused capacity, commitment fee (as a percent)				0.25%
Amount of debt outstanding							$ 0
Secured Revolving Promissory Note \| Private Loan Fund II
Related Party Transaction [Line Items]
Amounts of transaction		$ 50,000,000
Unused capacity, commitment fee (as a percent)		0.25%
Amount of debt outstanding							11,000,000
Secured Revolving Promissory Note \| Private Loan Fund II \| SOFR
Related Party Transaction [Line Items]
Interest rate (as a percent)		3.50%
Interest rate, floor (as a percent)		2.00%
2015 Deferred Compensation Plan
Related Party Transaction [Line Items]
Amounts of transaction							18,900,000
2015 Deferred Compensation Plan \| Rabbi Trust
Related Party Transaction [Line Items]
Amounts of transaction							$ 11,800,000
2015 Deferred Compensation Plan \| Common Stock
Related Party Transaction [Line Items]
Deferred compensation (in shares)		174,089					174,089
2015 Deferred Compensation Plan \| Phantom Stock Units
Related Party Transaction [Line Items]
Amounts of transaction							$ 7,100,000
2015 Deferred Compensation Plan \| Private Loan Fund \| Rabbi Trust
Related Party Transaction [Line Items]
Amounts of transaction							2,100,000
2015 Deferred Compensation Plan \| Private Loan Fund II \| Rabbi Trust
Related Party Transaction [Line Items]
Amounts of transaction							$ 800,000