Investments - Geographic Investment (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2025	Sep. 30, 2025	Dec. 31, 2024
Schedule of Investments [Line Items]
Cost		$ 13,932,697	$ 13,193,219
Fair Value		$ 13,809,636	$ 13,092,518
Fair Value as % of Net Assets		220.30%	215.50%
Investment Owned, At Fair Value | Investment Type Concentration Risk
Schedule of Investments [Line Items]
Concentration Risk, Percentage	100.00%	100.00%	100.00%
United States
Schedule of Investments [Line Items]
Cost		$ 12,342,319	$ 11,663,322
Fair Value		$ 12,172,029	$ 11,595,231
Fair Value as % of Net Assets		194.10%	190.80%
United States | Investment Owned, At Fair Value | Investment Type Concentration Risk
Schedule of Investments [Line Items]
Concentration Risk, Percentage		88.10%	88.60%
Europe
Schedule of Investments [Line Items]
Cost		$ 1,310,737	$ 1,138,542
Fair Value		$ 1,355,429	$ 1,104,837
Fair Value as % of Net Assets		21.60%	18.20%
Europe | Investment Owned, At Fair Value | Investment Type Concentration Risk
Schedule of Investments [Line Items]
Concentration Risk, Percentage		9.80%	8.40%
Bermuda/Cayman Islands
Schedule of Investments [Line Items]
Cost		$ 148,564	$ 149,595
Fair Value		$ 149,373	$ 149,735
Fair Value as % of Net Assets		2.40%	2.50%
Bermuda/Cayman Islands | Investment Owned, At Fair Value | Investment Type Concentration Risk
Schedule of Investments [Line Items]
Concentration Risk, Percentage		1.10%	1.20%
Canada
Schedule of Investments [Line Items]
Cost		$ 119,169	$ 241,124
Fair Value		$ 120,688	$ 242,103
Fair Value as % of Net Assets		2.00%	4.00%
Canada | Investment Owned, At Fair Value | Investment Type Concentration Risk
Schedule of Investments [Line Items]
Concentration Risk, Percentage		0.90%	1.80%
Asia
Schedule of Investments [Line Items]
Cost		$ 11,908	$ 636
Fair Value		$ 12,117	$ 612
Fair Value as % of Net Assets		0.20%	0.00%
Asia | Investment Owned, At Fair Value | Investment Type Concentration Risk
Schedule of Investments [Line Items]
Concentration Risk, Percentage		0.10%	0.00%