Commitments and Contingencies - Schedule of Unfunded Commitments by Investment (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Sep. 30, 2025
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	$ 957,189	$ 931,496
Investment, Identifier [Axis]: 107-109 Beech OAK22 LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	9,128	8,544
Investment, Identifier [Axis]: ACP Falcon Buyer Inc
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	5,333	5,333
Investment, Identifier [Axis]: ASP Integrity Acquisition Co LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	14,560	15,956
Investment, Identifier [Axis]: ASP-R-PAC Acquisition Co LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	129	153
Investment, Identifier [Axis]: AVSC Holding Corp.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	11,910	12,016
Investment, Identifier [Axis]: Atlas Borrower, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	9,883	9,883
Investment, Identifier [Axis]: Bamboo Ide8 Insurance Services, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	4,794	0
Investment, Identifier [Axis]: Bamboo US Bidco LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	5,302	8,701
Investment, Identifier [Axis]: Bayou Intermediate II, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	12,017	16,209
Investment, Identifier [Axis]: BioXcel Therapeutics, Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	0	3,577
Investment, Identifier [Axis]: Biscuit Parent, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	23,291	31,037
Investment, Identifier [Axis]: Blue Bidco Ltd
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	2,229	2,229
Investment, Identifier [Axis]: Centralsquare Technologies, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	3,302	3,302
Investment, Identifier [Axis]: Cielo Bidco Limited
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	3,016	5,947
Investment, Identifier [Axis]: Coupa Holdings, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	2,122	2,122
Investment, Identifier [Axis]: Creek Parent, Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	15,207	15,207
Investment, Identifier [Axis]: Crewline Buyer, Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	4,573	4,573
Investment, Identifier [Axis]: Draken International, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	22,175	22,175
Investment, Identifier [Axis]: Dukes Root Control Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	1,906	1,906
Investment, Identifier [Axis]: Empire Bidco AB
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	45,163	45,163
Investment, Identifier [Axis]: Enverus Holdings, Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	25,857	4,664
Investment, Identifier [Axis]: Everbridge, Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	19,899	19,899
Investment, Identifier [Axis]: Evergreen IX Borrower 2023, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	4,006	4,006
Investment, Identifier [Axis]: Eyesouth Eye Care Holdco LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	5	2,069
Investment, Identifier [Axis]: F&M BUYER LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	11,435	11,435
Investment, Identifier [Axis]: Flexera Software LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	3,129	3,129
Investment, Identifier [Axis]: Galileo Parent, Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	3,312	3,463
Investment, Identifier [Axis]: Geo Topco Corporation
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	16,500	16,500
Investment, Identifier [Axis]: Grand River Aseptic Manufacturing, Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	9,237	9,237
Investment, Identifier [Axis]: Grove Hotel Parcel Owner, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	884	1,768
Investment, Identifier [Axis]: IW Buyer LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	5,180	6,252
Investment, Identifier [Axis]: Icefall Parent, Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	5,144	5,144
Investment, Identifier [Axis]: Integrity Marketing Acquisition, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	24,486	26,386
Investment, Identifier [Axis]: Inventus Power, Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	4,967	3,808
Investment, Identifier [Axis]: Janus Bidco Limited
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	15,760	15,760
Investment, Identifier [Axis]: Jeppesen Holdings, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	3,312	0
Investment, Identifier [Axis]: Kairos Intermediateco AB
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	26,683	9,092
Investment, Identifier [Axis]: Kings Buyer, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	5,351	5,914
Investment, Identifier [Axis]: Kite Midco II Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	9,609	9,609
Investment, Identifier [Axis]: LDS Buyer, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	22,057	24,418
Investment, Identifier [Axis]: LSL Holdco, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	406	325
Investment, Identifier [Axis]: Legends Hospitality Holding Company, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	3,964	6,142
Investment, Identifier [Axis]: Lightbox Intermediate, L.P.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	3,752	3,845
Investment, Identifier [Axis]: MRI Software LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	12,845	5,313
Investment, Identifier [Axis]: MRO Florida, Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	1,856	0
Investment, Identifier [Axis]: Microf Funding V LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	9,992	9,992
Investment, Identifier [Axis]: Minotaur Acquisition, Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	4,174	11,132
Investment, Identifier [Axis]: Monotype Imaging Holdings Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	13,501	13,501
Investment, Identifier [Axis]: Monroe Engineering Group LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	9,584	0
Investment, Identifier [Axis]: NFM & J, L.P.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	3,019	14,982
Investment, Identifier [Axis]: Nellson Nutraceutical, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	10,524	11,283
Investment, Identifier [Axis]: Neptune Bidco US Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	6,863	6,863
Investment, Identifier [Axis]: Next Holdco, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	16,443	16,443
Investment, Identifier [Axis]: North Star Acquisitionco, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	10,937	9,282
Investment, Identifier [Axis]: OneOncology, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	42,199	29,986
Investment, Identifier [Axis]: Optimizely North America Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	7,109	7,109
Investment, Identifier [Axis]: PAI Financing Merger Sub LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	13,534	15,790
Investment, Identifier [Axis]: PPW Aero Buyer, Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	64,606	64,950
Investment, Identifier [Axis]: PetVet Care Centers, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	8,645	19,210
Investment, Identifier [Axis]: Pike Corporation
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	27,696	0
Investment, Identifier [Axis]: Pluralsight, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	3,351	3,351
Investment, Identifier [Axis]: Poseidon Midco AB
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	33,349	32,131
Investment, Identifier [Axis]: Premium Parent, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	9,264	0
Investment, Identifier [Axis]: Project Accelerate Parent, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	6,250	6,250
Investment, Identifier [Axis]: Propio LS, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	576	1,029
Investment, Identifier [Axis]: Protein for Pets Opco, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	5,311	4,847
Investment, Identifier [Axis]: RWK Midco AB
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	29,292	35,762
Investment, Identifier [Axis]: SEI Holding I Corporation
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	14,400	14,400
Investment, Identifier [Axis]: Sierra Enterprises, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	7,264	7,264
Investment, Identifier [Axis]: Silk Holdings III LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	1,940	0
Investment, Identifier [Axis]: Sorenson Communications, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	10,177	10,177
Investment, Identifier [Axis]: Spruce Bidco I Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	26,341	26,341
Investment, Identifier [Axis]: SumUp Holdings Luxembourg
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	0	12,795
Investment, Identifier [Axis]: TBRS, Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	14,113	13,697
Investment, Identifier [Axis]: THG Acquisition, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	12,948	14,729
Investment, Identifier [Axis]: Transit Buyer LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	1,555	1,950
Investment, Identifier [Axis]: Truck-Lite Co., LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	30,364	32,010
Investment, Identifier [Axis]: US WorldMeds Ventures, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	15,892	15,892
Investment, Identifier [Axis]: USIC Holdings, Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	4,297	5,324
Investment, Identifier [Axis]: Verona Pharma, Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	0	9,011
Investment, Identifier [Axis]: Violin Finco Guernsey Limited
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	3,933	3,933
Investment, Identifier [Axis]: WP CPP Holdings, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	5,831	5,831
Investment, Identifier [Axis]: West Star Aviation Acquisition LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	15,264	21,278
Investment, Identifier [Axis]: Whitney Merger Sub, Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	9,771	9,772
Investment, Identifier [Axis]: eShipping, LLC
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	10,283	0
Investment, Identifier [Axis]: iCIMs, Inc.
Financial Support for Nonconsolidated Legal Entity [Line Items]
Unfunded Commitment	$ 921	$ 988