Investments - SLP's portfolio (Details) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2023 USD ($) Borrower	Dec. 31, 2022 USD ($) Borrower
Concentration Risk [Line Items]
Investments at fair value	$ 2,385,272	$ 2,386,977
Bain Capital Senior Loan Program, LLC
Concentration Risk [Line Items]
Investments at fair value	$ 830,104	$ 546,654
Weighted average yield on investments	11.50%	10.60%
Number of borrowers in ISLP | Borrower	60	48
Unfunded commitments	$ 1,628	$ 1,838
Bain Capital Senior Loan Program, LLC | Investments Operations [Member] | Investment Concentration Risk [Member] | Largest Investee [Member]
Concentration Risk [Line Items]
Investments at fair value	32,532	23,016
Bain Capital Senior Loan Program, LLC | Investments Operations [Member] | Investment Concentration Risk [Member] | Five Largest Investee [Member]
Concentration Risk [Line Items]
Investments at fair value	$ 147,880	$ 111,597