v3.26.3
Janus Henderson Small-Mid Cap Value Fund Average Annual Total Returns - Class A C S I N T Shares [Member]
 12 Months Ended 60 Months Ended 120 Months Ended 169 Months Ended
Jun. 30, 2026
Dec. 31, 2025
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 A | Return Before Taxes[Member]          
Prospectus [Line Items]          
Average Annual Return, Percent [1]   (1.76%) 6.68% 7.82%  
Class C | Return Before Taxes[Member]          
Prospectus [Line Items]          
Average Annual Return, Percent [2]   2.46% 7.16% 7.65%  
Class S | Return Before Taxes[Member]          
Prospectus [Line Items]          
Average Annual Return, Percent   4.21% 7.92% 8.44%  
Class I | After Taxes on Distributions          
Prospectus [Line Items]          
Average Annual Return, Percent   2.26% 7.14% 7.28%  
Class I | After Taxes on Distributions and Sales          
Prospectus [Line Items]          
Average Annual Return, Percent [3]   4.08% 6.38% 6.78%  
Class I | Return Before Taxes[Member]          
Prospectus [Line Items]          
Average Annual Return, Percent   4.46% 8.22% 8.74%  
Performance Inception Date Aug. 04, 2017        
Class N | Return Before Taxes[Member]          
Prospectus [Line Items]          
Average Annual Return, Percent   4.59% 8.34% 9.37%
Class T | Return Before Taxes[Member]          
Prospectus [Line Items]          
Average Annual Return, Percent   4.31% 8.06% 8.58%  
[1] Calculated assuming maximum permitted sales loads.
[2] The one year return is calculated to include the contingent deferred sales charge.
[3] 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.