Quarterly report [Sections 13 or 15(d)]

Investments - Schedule of Fair Value Portfolio by Industry Sector (Details)

v3.25.1
Investments - Schedule of Fair Value Portfolio by Industry Sector (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Mar. 31, 2025
Dec. 31, 2024
Schedule Of Investments [Line Items]    
Investments at Fair Value $ 3,924,450 $ 3,659,978
Industry Sector Concentration Risk | Total Industry Sectors    
Schedule Of Investments [Line Items]    
Investments at Fair Value 3,924,450 3,659,978
Industry Sector Concentration Risk | Software    
Schedule Of Investments [Line Items]    
Investments at Fair Value 1,262,813 1,081,100
Industry Sector Concentration Risk | Drug Discovery & Development    
Schedule Of Investments [Line Items]    
Investments at Fair Value 1,119,941 1,080,390
Industry Sector Concentration Risk | Healthcare Services, Other    
Schedule Of Investments [Line Items]    
Investments at Fair Value 625,556 610,184
Industry Sector Concentration Risk | Consumer & Business Services    
Schedule Of Investments [Line Items]    
Investments at Fair Value 374,561 372,641
Industry Sector Concentration Risk | Electronics & Computer Hardware    
Schedule Of Investments [Line Items]    
Investments at Fair Value 167,370 162,888
Industry Sector Concentration Risk | Diversified Financial Services    
Schedule Of Investments [Line Items]    
Investments at Fair Value 117,366 113,491
Industry Sector Concentration Risk | Medical Devices & Equipment    
Schedule Of Investments [Line Items]    
Investments at Fair Value 75,238 74,962
Industry Sector Concentration Risk | Space Technologies    
Schedule Of Investments [Line Items]    
Investments at Fair Value 49,527 45,700
Industry Sector Concentration Risk | Biotechnology Tools    
Schedule Of Investments [Line Items]    
Investments at Fair Value 34,819 35,434
Industry Sector Concentration Risk | Communications & Networking    
Schedule Of Investments [Line Items]    
Investments at Fair Value 27,601 27,700
Industry Sector Concentration Risk | Information Services    
Schedule Of Investments [Line Items]    
Investments at Fair Value 24,923 24,356
Industry Sector Concentration Risk | Sustainable and Renewable Technology    
Schedule Of Investments [Line Items]    
Investments at Fair Value 22,396 27,696
Industry Sector Concentration Risk | Manufacturing Technology    
Schedule Of Investments [Line Items]    
Investments at Fair Value 20,653 1,162
Industry Sector Concentration Risk | Consumer & Business Products    
Schedule Of Investments [Line Items]    
Investments at Fair Value 1,139 1,497
Industry Sector Concentration Risk | Semiconductors    
Schedule Of Investments [Line Items]    
Investments at Fair Value 425 704
Industry Sector Concentration Risk | Media/Content/Info    
Schedule Of Investments [Line Items]    
Investments at Fair Value 114 63
Industry Sector Concentration Risk | Drug Delivery    
Schedule Of Investments [Line Items]    
Investments at Fair Value $ 8 $ 10
Industry Sector Concentration Risk | Industry Sector Investments Benchmark | Total Industry Sectors    
Schedule Of Investments [Line Items]    
Percentage of Total Portfolio 100.00% 100.00%
Industry Sector Concentration Risk | Industry Sector Investments Benchmark | Software    
Schedule Of Investments [Line Items]    
Percentage of Total Portfolio 32.20% 29.50%
Industry Sector Concentration Risk | Industry Sector Investments Benchmark | Drug Discovery & Development    
Schedule Of Investments [Line Items]    
Percentage of Total Portfolio 28.50% 29.50%
Industry Sector Concentration Risk | Industry Sector Investments Benchmark | Healthcare Services, Other    
Schedule Of Investments [Line Items]    
Percentage of Total Portfolio 15.90% 16.70%
Industry Sector Concentration Risk | Industry Sector Investments Benchmark | Consumer & Business Services    
Schedule Of Investments [Line Items]    
Percentage of Total Portfolio 9.60% 10.20%
Industry Sector Concentration Risk | Industry Sector Investments Benchmark | Electronics & Computer Hardware    
Schedule Of Investments [Line Items]    
Percentage of Total Portfolio 4.30% 4.50%
Industry Sector Concentration Risk | Industry Sector Investments Benchmark | Diversified Financial Services    
Schedule Of Investments [Line Items]    
Percentage of Total Portfolio 3.00% 3.10%
Industry Sector Concentration Risk | Industry Sector Investments Benchmark | Medical Devices & Equipment    
Schedule Of Investments [Line Items]    
Percentage of Total Portfolio 1.90% 2.00%
Industry Sector Concentration Risk | Industry Sector Investments Benchmark | Space Technologies    
Schedule Of Investments [Line Items]    
Percentage of Total Portfolio 1.30% 1.20%
Industry Sector Concentration Risk | Industry Sector Investments Benchmark | Biotechnology Tools    
Schedule Of Investments [Line Items]    
Percentage of Total Portfolio 0.90% 1.00%
Industry Sector Concentration Risk | Industry Sector Investments Benchmark | Communications & Networking    
Schedule Of Investments [Line Items]    
Percentage of Total Portfolio 0.70% 0.80%
Industry Sector Concentration Risk | Industry Sector Investments Benchmark | Information Services    
Schedule Of Investments [Line Items]    
Percentage of Total Portfolio 0.60% 0.70%
Industry Sector Concentration Risk | Industry Sector Investments Benchmark | Sustainable and Renewable Technology    
Schedule Of Investments [Line Items]    
Percentage of Total Portfolio 0.60% 0.80%
Industry Sector Concentration Risk | Industry Sector Investments Benchmark | Manufacturing Technology    
Schedule Of Investments [Line Items]    
Percentage of Total Portfolio 0.50% 0.00%
Industry Sector Concentration Risk | Industry Sector Investments Benchmark | Consumer & Business Products    
Schedule Of Investments [Line Items]    
Percentage of Total Portfolio 0.00% 0.00%
Industry Sector Concentration Risk | Industry Sector Investments Benchmark | Semiconductors    
Schedule Of Investments [Line Items]    
Percentage of Total Portfolio 0.00% 0.00%
Industry Sector Concentration Risk | Industry Sector Investments Benchmark | Media/Content/Info    
Schedule Of Investments [Line Items]    
Percentage of Total Portfolio 0.00% 0.00%
Industry Sector Concentration Risk | Industry Sector Investments Benchmark | Drug Delivery    
Schedule Of Investments [Line Items]    
Percentage of Total Portfolio 0.00% 0.00%