Janus Henderson Mid Cap Value Portfolio Annual Fund Operating Expenses - Institutional Shares [Member] - Janus Henderson Mid Cap Value Portfolio	Dec. 31, 2025
Prospectus [Line Items]
Fee Waiver or Reimbursement over Assets, Date of Termination	<span style="font-family:Times New Roman;font-size:7.60pt;">The Adviser has contractually agreed to waive its investment advisory fee and/or reimburse Portfolio expenses to the extent that the Portfolio’s total annual fund operating expenses (excluding any performance adjustments to management fees, shareholder servicing fees, out-of-pocket transfer agency/shareholder servicing costs, acquired fund fees and expenses, interest, dividends, taxes, brokerage commissions, and extraordinary expenses) exceed 0.77% for at least a one-year period commencing on April 30, 2026. This contractual waiver may be terminated or modified only at the discretion of the Portfolio’s Board of Trustees.</span>
Institutional Shares
Prospectus [Line Items]
Management Fees (as a percentage of Assets)	0.65%	[1]
Other Expenses (as a percentage of Assets):	0.21%
Expenses (as a percentage of Assets)	0.86%
Fee Waiver or Reimbursement	(0.03%)	[2]
Net Expenses (as a percentage of Assets)	0.83%	[2]

[1] This fee may adjust up or down monthly based on the Portfolio’s performance relative to its benchmark index over the performance measurement period. For more information regarding performance-based advisory fees, refer to “Management Expenses” in the Portfolio’s Prospectus.

[2] The Adviser has contractually agreed to waive its investment advisory fee and/or reimburse Portfolio expenses to the extent that the Portfolio’s total annual fund operating expenses (excluding any performance adjustments to management fees, shareholder servicing fees, out-of-pocket transfer agency/shareholder servicing costs, acquired fund fees and expenses, interest, dividends, taxes, brokerage commissions, and extraordinary expenses) exceed 0.77% for at least a one-year period commencing on April 30, 2026. This contractual waiver may be terminated or modified only at the discretion of the Portfolio’s Board of Trustees.