Investments - Schedule of Composition of Investment Portfolio (Detail) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Schedule of Investments [Line Items]
Investment cost	$ 3,357,777	$ 3,177,397
Fair Value	3,188,621	3,014,416
Total Investments before Cash Equivalents	3,357,777
Total Investments before Cash Equivalents, Fair Value	3,188,621
Total Cash Equivalents	1,853	2,810
Total Cash Equivalents, Fair Value	1,853	2,810
Total Investments after Cash Equivalents	3,359,630	3,180,207
Total Investments after Cash Equivalents, Fair Value	3,190,474	3,017,226
Foreign currency forward transactions, Fair Value	33
Total Assets and Liabilities at Fair Value	3,359,630
Total Assets and Liabilities at Fair Value, Fair Value	3,190,507
Money Market Funds [Member]
Schedule of Investments [Line Items]
Total Cash Equivalents	1,853	2,810
Total Cash Equivalents, Fair Value	1,853	2,810
Level 1
Schedule of Investments [Line Items]
Fair Value		220
Total Investments before Cash Equivalents, Fair Value	283
Total Cash Equivalents, Fair Value	1,853	2,810
Total Investments after Cash Equivalents, Fair Value	2,136	3,030
Total Assets and Liabilities at Fair Value, Fair Value	2,136
Level 1 | Money Market Funds [Member]
Schedule of Investments [Line Items]
Total Cash Equivalents, Fair Value	1,853	2,810
Level 2
Schedule of Investments [Line Items]
Fair Value		119,346
Total Investments before Cash Equivalents, Fair Value	80,547
Total Investments after Cash Equivalents, Fair Value	80,547	119,346
Foreign currency forward transactions, Fair Value	33
Total Assets and Liabilities at Fair Value, Fair Value	80,580
Level 3
Schedule of Investments [Line Items]
Fair Value		2,894,850
Total Investments before Cash Equivalents, Fair Value	3,107,791
Total Investments after Cash Equivalents, Fair Value	3,107,791	2,894,850
Total Assets and Liabilities at Fair Value, Fair Value	3,107,791
First Lien Secured Debt
Schedule of Investments [Line Items]
Investment cost		2,804,070
Fair Value		2,765,156
Total Investments before Cash Equivalents	2,997,085
Total Investments before Cash Equivalents, Fair Value	2,954,954
First Lien Secured Debt | Level 2
Schedule of Investments [Line Items]
Fair Value		88,903
Total Investments before Cash Equivalents, Fair Value	58,230
First Lien Secured Debt | Level 3
Schedule of Investments [Line Items]
Fair Value		2,676,253
Total Investments before Cash Equivalents, Fair Value	2,896,724
Second Lien Secured Debt
Schedule of Investments [Line Items]
Investment cost		23,454
Fair Value		17,798
Total Investments before Cash Equivalents	14,983
Total Investments before Cash Equivalents, Fair Value	8,345
Second Lien Secured Debt | Level 2
Schedule of Investments [Line Items]
Fair Value		12,034
Total Investments before Cash Equivalents, Fair Value	4,124
Second Lien Secured Debt | Level 3
Schedule of Investments [Line Items]
Fair Value		5,764
Total Investments before Cash Equivalents, Fair Value	4,221
Unsecured Debt
Schedule of Investments [Line Items]
Investment cost		6,059
Fair Value		3,502
Total Investments before Cash Equivalents	6,080
Total Investments before Cash Equivalents, Fair Value	3,409
Unsecured Debt | Level 2
Schedule of Investments [Line Items]
Fair Value		3,385
Total Investments before Cash Equivalents, Fair Value	3,300
Unsecured Debt | Level 3
Schedule of Investments [Line Items]
Fair Value		117
Total Investments before Cash Equivalents, Fair Value	109
Structured Products And Other
Schedule of Investments [Line Items]
Investment cost		53,671
Fair Value		41,125
Total Investments before Cash Equivalents	51,491
Total Investments before Cash Equivalents, Fair Value	38,385
Structured Products And Other | Level 2
Schedule of Investments [Line Items]
Fair Value		15,024
Total Investments before Cash Equivalents, Fair Value	14,893
Structured Products And Other | Level 3
Schedule of Investments [Line Items]
Fair Value		26,101
Total Investments before Cash Equivalents, Fair Value	23,492
Preferred Equity
Schedule of Investments [Line Items]
Investment cost		16,069
Fair Value		24,831
Total Investments before Cash Equivalents	15,917
Total Investments before Cash Equivalents, Fair Value	23,664
Preferred Equity | Level 3
Schedule of Investments [Line Items]
Fair Value		24,831
Total Investments before Cash Equivalents, Fair Value	23,664
Common Equity/Interests
Schedule of Investments [Line Items]
Investment cost		273,109
Fair Value		161,868
Total Investments before Cash Equivalents	271,256
Total Investments before Cash Equivalents, Fair Value	159,649
Common Equity/Interests | Level 1
Schedule of Investments [Line Items]
Fair Value		220
Total Investments before Cash Equivalents, Fair Value	283
Common Equity/Interests | Level 3
Schedule of Investments [Line Items]
Fair Value		161,648
Total Investments before Cash Equivalents, Fair Value	159,366
Warrants - Warrants
Schedule of Investments [Line Items]
Investment cost		965
Fair Value		136
Total Investments before Cash Equivalents	965
Total Investments before Cash Equivalents, Fair Value	215
Warrants - Warrants | Level 3
Schedule of Investments [Line Items]
Fair Value		$ 136
Total Investments before Cash Equivalents, Fair Value	$ 215