v3.26.3
Janus Henderson Mid Cap Value Fund Average Annual Total Returns - Class A C S I N R T 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 Midcap® Value Index (reflects no deduction for expenses, fees, or taxes)[Member]      
Prospectus [Line Items]      
Average Annual Return, Percent 11.05% 9.83% 9.78%
Class A | Return Before Taxes[Member]      
Prospectus [Line Items]      
Average Annual Return, Percent [1] 0.46% 7.30% 7.78%
Class C | Return Before Taxes[Member]      
Prospectus [Line Items]      
Average Annual Return, Percent [2] 4.82% 7.85% 7.74%
Class S | Return Before Taxes[Member]      
Prospectus [Line Items]      
Average Annual Return, Percent 6.38% 8.46% 8.34%
Class I | Return Before Taxes[Member]      
Prospectus [Line Items]      
Average Annual Return, Percent 6.84% 8.89% 8.76%
Class N | Return Before Taxes[Member]      
Prospectus [Line Items]      
Average Annual Return, Percent 6.94% 9.01% 8.88%
Class R | Return Before Taxes[Member]      
Prospectus [Line Items]      
Average Annual Return, Percent 6.18% 8.20% 8.07%
Class T | After Taxes on Distributions      
Prospectus [Line Items]      
Average Annual Return, Percent 4.31% 6.46% 6.52%
Class T | After Taxes on Distributions and Sales      
Prospectus [Line Items]      
Average Annual Return, Percent [3] 5.43% 6.63% 6.55%
Class T | Return Before Taxes[Member]      
Prospectus [Line Items]      
Average Annual Return, Percent 6.70% 8.75% 8.62%
[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.