Investments - Investments By Geographic Region (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Consolidated Schedule of Investments
Investments, amortized cost	$ 2,356,143	$ 2,311,384
Percentage of Total Portfolio	100.00%	100.00%
Market Value	$ 2,293,522	$ 2,289,105
Percentage of Total Portfolio	100.00%	100.00%
United States
Consolidated Schedule of Investments
Investments, amortized cost	$ 2,054,218	$ 2,071,058
Percentage of Total Portfolio	87.20%	89.50%
Market Value	$ 2,005,137	$ 2,061,372
Percentage of Total Portfolio	87.40%	90.00%
Cayman Islands
Consolidated Schedule of Investments
Investments, amortized cost	$ 114,115	$ 116,916
Percentage of Total Portfolio	5.00%	5.10%
Market Value	$ 113,796	$ 101,888
Percentage of Total Portfolio	5.10%	4.50%
United Kingdom
Consolidated Schedule of Investments
Investments, amortized cost	$ 81,284	$ 41,736
Percentage of Total Portfolio	3.40%	1.80%
Market Value	$ 74,077	$ 43,658
Percentage of Total Portfolio	3.20%	1.90%
Luxembourg
Consolidated Schedule of Investments
Investments, amortized cost	$ 26,833	$ 24,848
Percentage of Total Portfolio	1.10%	1.10%
Market Value	$ 25,984	$ 24,973
Percentage of Total Portfolio	1.10%	1.10%
Germany
Consolidated Schedule of Investments
Investments, amortized cost	$ 18,833	$ 20,657
Percentage of Total Portfolio	0.80%	0.90%
Market Value	$ 18,847	$ 20,352
Percentage of Total Portfolio	0.80%	0.90%
Canada
Consolidated Schedule of Investments
Investments, amortized cost	$ 19,146	$ 2,195
Percentage of Total Portfolio	0.80%	0.10%
Market Value	$ 16,838	$ 2,232
Percentage of Total Portfolio	0.70%	0.10%
Australia
Consolidated Schedule of Investments
Investments, amortized cost	$ 11,036	$ 217
Percentage of Total Portfolio	0.50%	0.00%
Market Value	$ 12,024	$ 66
Percentage of Total Portfolio	0.50%	0.00%
Ireland
Consolidated Schedule of Investments
Investments, amortized cost	$ 12,087	$ 27,315
Percentage of Total Portfolio	0.50%	1.20%
Market Value	$ 10,512	$ 28,050
Percentage of Total Portfolio	0.50%	1.20%
Netherlands
Consolidated Schedule of Investments
Investments, amortized cost	$ 8,125
Percentage of Total Portfolio	0.30%
Market Value	$ 6,671
Percentage of Total Portfolio	0.30%
Guernsey
Consolidated Schedule of Investments
Investments, amortized cost	$ 5,160	$ 3,499
Percentage of Total Portfolio	0.20%	0.20%
Market Value	$ 4,646	$ 3,528
Percentage of Total Portfolio	0.20%	0.20%
Belgium
Consolidated Schedule of Investments
Investments, amortized cost	$ 4,780	$ 2,372
Percentage of Total Portfolio	0.20%	0.10%
Market Value	$ 4,503	$ 2,424
Percentage of Total Portfolio	0.20%	0.10%
Israel
Consolidated Schedule of Investments
Investments, amortized cost	$ 341	$ 386
Percentage of Total Portfolio	0.00%	0.00%
Market Value	$ 344	$ 391
Percentage of Total Portfolio	0.00%	0.00%
Sweden
Consolidated Schedule of Investments
Investments, amortized cost	$ 185	$ 185
Percentage of Total Portfolio	0.00%	0.00%
Market Value	$ 143	$ 171
Percentage of Total Portfolio	0.00%	0.00%