v3.26.3
Janus Henderson Small-Mid Cap Value Fund Average Annual Total Returns - Class D Shares [Member]
 12 Months Ended 60 Months Ended 120 Months Ended
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Russell 3000® Index (reflects no deduction for expenses, fees, or taxes)[Member]      
Prospectus [Line Items]      
Average Annual Return, Percent 17.15% 13.15% 14.29%
Russell 2500™ Value Index (reflects no deduction for expenses, fees, or taxes)[Member]      
Prospectus [Line Items]      
Average Annual Return, Percent 12.73% 10.02% 9.72%
Class D | After Taxes on Distributions      
Prospectus [Line Items]      
Average Annual Return, Percent 2.21% 7.10% 7.22%
Class D | After Taxes on Distributions and Sales      
Prospectus [Line Items]      
Average Annual Return, Percent [1] 4.08% 6.36% 6.73%
Class D | Return Before Taxes[Member]      
Prospectus [Line Items]      
Average Annual Return, Percent 4.43% 8.19% 8.69%
[1] If the Fund incurs a loss, which generates a tax benefit, the Return After Taxes on Distributions and Sale of Fund Shares may exceed the Fund’s other return figures.