Investments - Schedule of Composition of Investments Based on Fair Value (Details) - Investment Owned, At Fair Value	9 Months Ended	12 Months Ended
	Sep. 30, 2025	Dec. 31, 2024
Industry Concentration Risk
Schedule of Investments [Line Items]
Concentration risk (as percent)	100.00%	100.00%
Industry Concentration Risk \| Advertising and media
Schedule of Investments [Line Items]
Concentration risk (as percent)	2.60%	2.50%
Industry Concentration Risk \| Aerospace and defense
Schedule of Investments [Line Items]
Concentration risk (as percent)	1.00%	2.90%
Industry Concentration Risk \| Asset Based Lending and Fund Finance
Schedule of Investments [Line Items]
Concentration risk (as percent)	1.80%	1.20%
Industry Concentration Risk \| Automotive Services
Schedule of Investments [Line Items]
Concentration risk (as percent)	3.10%	2.20%
Industry Concentration Risk \| Buildings and real estate
Schedule of Investments [Line Items]
Concentration risk (as percent)	4.70%	3.50%
Industry Concentration Risk \| Business services
Schedule of Investments [Line Items]
Concentration risk (as percent)	2.80%	3.10%
Industry Concentration Risk \| Chemicals
Schedule of Investments [Line Items]
Concentration risk (as percent)	4.70%	4.20%
Industry Concentration Risk \| Consumer products
Schedule of Investments [Line Items]
Concentration risk (as percent)	2.80%	5.00%
Industry Concentration Risk \| Containers and packaging
Schedule of Investments [Line Items]
Concentration risk (as percent)	2.20%	1.80%
Industry Concentration Risk \| Distribution
Schedule of Investments [Line Items]
Concentration risk (as percent)	3.50%	3.00%
Industry Concentration Risk \| Education
Schedule of Investments [Line Items]
Concentration risk (as percent)	0.70%	0.60%
Industry Concentration Risk \| Energy equipment and services
Schedule of Investments [Line Items]
Concentration risk (as percent)	0.60%	0.50%
Industry Concentration Risk \| Financial services
Schedule of Investments [Line Items]
Concentration risk (as percent)	3.50%	3.30%
Industry Concentration Risk \| Food and beverage
Schedule of Investments [Line Items]
Concentration risk (as percent)	7.60%	8.40%
Industry Concentration Risk \| Healthcare equipment and services
Schedule of Investments [Line Items]
Concentration risk (as percent)	3.50%	2.90%
Industry Concentration Risk \| Healthcare providers and services
Schedule of Investments [Line Items]
Concentration risk (as percent)	8.80%	7.20%
Industry Concentration Risk \| Healthcare technology
Schedule of Investments [Line Items]
Concentration risk (as percent)	6.70%	8.00%
Industry Concentration Risk \| Household products
Schedule of Investments [Line Items]
Concentration risk (as percent)	2.30%	1.90%
Industry Concentration Risk \| Human resource support services
Schedule of Investments [Line Items]
Concentration risk (as percent)	1.90%	1.50%
Industry Concentration Risk \| Infrastructure and environmental services
Schedule of Investments [Line Items]
Concentration risk (as percent)	0.80%	1.20%
Industry Concentration Risk \| Insurance
Schedule of Investments [Line Items]
Concentration risk (as percent)	1.70%	6.50%
Industry Concentration Risk \| Internet software and services
Schedule of Investments [Line Items]
Concentration risk (as percent)	12.00%	10.10%
Industry Concentration Risk \| Joint ventures
Schedule of Investments [Line Items]
Concentration risk (as percent)	0.00%	0.00%
Industry Concentration Risk \| Leisure and entertainment
Schedule of Investments [Line Items]
Concentration risk (as percent)	2.30%	2.20%
Industry Concentration Risk \| Manufacturing
Schedule of Investments [Line Items]
Concentration risk (as percent)	9.20%	8.10%
Industry Concentration Risk \| Pharmaceuticals
Schedule of Investments [Line Items]
Concentration risk (as percent)	0.70%	0.50%
Industry Concentration Risk \| Professional services
Schedule of Investments [Line Items]
Concentration risk (as percent)	2.90%	2.50%
Industry Concentration Risk \| Specialty retail
Schedule of Investments [Line Items]
Concentration risk (as percent)	3.80%	3.50%
Industry Concentration Risk \| Telecommunications
Schedule of Investments [Line Items]
Concentration risk (as percent)	0.40%	0.50%
Industry Concentration Risk \| Transportation
Schedule of Investments [Line Items]
Concentration risk (as percent)	1.40%	1.20%
Geographic Concentration Risk
Schedule of Investments [Line Items]
Concentration risk (as percent)	100.00%	100.00%
Geographic Concentration Risk \| Midwest
Schedule of Investments [Line Items]
Concentration risk (as percent)	21.60%	21.70%
Geographic Concentration Risk \| Northeast
Schedule of Investments [Line Items]
Concentration risk (as percent)	18.30%	15.50%
Geographic Concentration Risk \| South
Schedule of Investments [Line Items]
Concentration risk (as percent)	35.60%	30.00%
Geographic Concentration Risk \| West
Schedule of Investments [Line Items]
Concentration risk (as percent)	19.80%	25.40%
Geographic Concentration Risk \| International
Schedule of Investments [Line Items]
Concentration risk (as percent)	4.70%	7.40%

Blue Owl Capital Corp II 10-Q