Investments - Geographic Investment (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2023	Dec. 31, 2022
Schedule of Investments [Line Items]
Cost	$ 9,669,106	$ 9,657,872
Fair Value	$ 9,626,202	$ 9,617,248
Fair Value as % of Net Assets	229.72%	231.24%
Investment Owned, At Fair Value \| Investment Type Concentration Risk
Schedule of Investments [Line Items]
% of Total Investments at Fair Value	100.00%	100.00%
United States
Schedule of Investments [Line Items]
Cost	$ 8,983,241	$ 8,934,926
Fair Value	$ 8,929,026	$ 8,893,051
Fair Value as % of Net Assets	213.08%	213.83%
United States \| Investment Owned, At Fair Value \| Investment Type Concentration Risk
Schedule of Investments [Line Items]
% of Total Investments at Fair Value	92.76%	92.47%
Canada
Schedule of Investments [Line Items]
Cost	$ 470,555	$ 510,599
Fair Value	$ 486,555	$ 520,368
Fair Value as % of Net Assets	11.61%	12.51%
Canada \| Investment Owned, At Fair Value \| Investment Type Concentration Risk
Schedule of Investments [Line Items]
% of Total Investments at Fair Value	5.05%	5.41%
Europe
Schedule of Investments [Line Items]
Cost	$ 215,310	$ 212,347
Fair Value	$ 210,621	$ 203,829
Fair Value as % of Net Assets	5.03%	4.90%
Europe \| Investment Owned, At Fair Value \| Investment Type Concentration Risk
Schedule of Investments [Line Items]
% of Total Investments at Fair Value	2.19%	2.12%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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