v3.26.1
Shareholder Report
 6 Months Ended
Jun. 30, 2026
USD ($)
Holding
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name JANUS ASPEN SERIES
Entity Central Index Key 0000906185
Entity Investment Company Type N-1A
Document Period End Date Jun. 30, 2026
C000028717  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Balanced Portfolio
Class Name Institutional Shares
Trading Symbol JABLX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Balanced Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Balanced Portfolio (Institutional Shares/JABLX)
$31
0.62%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 31
Expense Ratio, Percent 0.62% [1]
AssetsNet $ 9,144,000,000
Holdings Count | Holding 727
InvestmentCompanyPortfolioTurnover 45.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$9,144
Number of portfolio holdingsFootnote Reference#
727
Portfolio turnover rate
45%
FootnoteDescription
Footnote#
Does not include derivatives, except purchased options, if any.
C000028716  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Balanced Portfolio
Class Name Service Shares
No Trading Symbol [Flag] true
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Balanced Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Balanced Portfolio (Service Shares)
$44
0.87%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 44
Expense Ratio, Percent 0.87% [2]
AssetsNet $ 9,144,000,000
Holdings Count | Holding 727
InvestmentCompanyPortfolioTurnover 45.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$9,144
Number of portfolio holdingsFootnote Reference#
727
Portfolio turnover rate
45%
FootnoteDescription
Footnote#
Does not include derivatives, except purchased options, if any.
C000028721  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Enterprise Portfolio
Class Name Institutional Shares
Trading Symbol JAAGX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Enterprise Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Enterprise Portfolio (Institutional Shares/JAAGX)
$37
0.71%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 37
Expense Ratio, Percent 0.71% [3]
AssetsNet $ 1,918,000,000
Holdings Count | Holding 83
InvestmentCompanyPortfolioTurnover 14.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$1,918
Number of portfolio holdingsFootnote Reference#
83
Portfolio turnover rate
14%
FootnoteDescription
Footnote#
Does not include derivatives, except purchased options, if any.
C000028720  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Enterprise Portfolio
Class Name Service Shares
No Trading Symbol [Flag] true
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Enterprise Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Enterprise Portfolio (Service Shares)
$50
0.96%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 50
Expense Ratio, Percent 0.96% [4]
AssetsNet $ 1,918,000,000
Holdings Count | Holding 83
InvestmentCompanyPortfolioTurnover 14.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$1,918
Number of portfolio holdingsFootnote Reference#
83
Portfolio turnover rate
14%
FootnoteDescription
Footnote#
Does not include derivatives, except purchased options, if any.
C000028734  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Flexible Bond Portfolio
Class Name Institutional Shares
Trading Symbol JAFLX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Flexible Bond Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Flexible Bond Portfolio (Institutional Shares/JAFLX)
$28
0.57%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 28
Expense Ratio, Percent 0.57% [5]
AssetsNet $ 619,000,000
Holdings Count | Holding 622
InvestmentCompanyPortfolioTurnover 101.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$619
Number of portfolio holdingsFootnote Reference#
622
Portfolio turnover rate
101%
Weighted average maturity
6.13 Years
Effective duration
5.76 Years
FootnoteDescription
Footnote#
Does not include derivatives, except purchased options, if any.
C000028733  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Flexible Bond Portfolio
Class Name Service Shares
No Trading Symbol [Flag] true
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Flexible Bond Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Flexible Bond Portfolio (Service Shares)
$40
0.81%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 40
Expense Ratio, Percent 0.81% [6]
AssetsNet $ 619,000,000
Holdings Count | Holding 622
InvestmentCompanyPortfolioTurnover 101.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$619
Number of portfolio holdingsFootnote Reference#
622
Portfolio turnover rate
101%
Weighted average maturity
6.13 Years
Effective duration
5.76 Years
FootnoteDescription
Footnote#
Does not include derivatives, except purchased options, if any.
C000028737  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Forty Portfolio
Class Name Institutional Shares
Trading Symbol JACAX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Forty Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Forty Portfolio (Institutional Shares/JACAX)
$28
0.55%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 28
Expense Ratio, Percent 0.55% [7]
AssetsNet $ 992,000,000
Holdings Count | Holding 36
InvestmentCompanyPortfolioTurnover 24.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$992
Number of portfolio holdings
36
Portfolio turnover rate
24%
C000028736  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Forty Portfolio
Class Name Service Shares
No Trading Symbol [Flag] true
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Forty Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Forty Portfolio (Service Shares)
$40
0.79%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 40
Expense Ratio, Percent 0.79% [8]
AssetsNet $ 992,000,000
Holdings Count | Holding 36
InvestmentCompanyPortfolioTurnover 24.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$992
Number of portfolio holdings
36
Portfolio turnover rate
24%
C000028730  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Global Research Portfolio
Class Name Institutional Shares
Trading Symbol JAWGX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Global Research Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Global Research Portfolio (Institutional Shares/JAWGX)
$41
0.79%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 41
Expense Ratio, Percent 0.79% [9]
AssetsNet $ 1,096,000,000
Holdings Count | Holding 120
InvestmentCompanyPortfolioTurnover 21.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$1,096
Number of portfolio holdings
120
Portfolio turnover rate
21%
C000028728  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Global Research Portfolio
Class Name Service Shares
No Trading Symbol [Flag] true
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Global Research Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Global Research Portfolio (Service Shares)
$54
1.04%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 54
Expense Ratio, Percent 1.04% [10]
AssetsNet $ 1,096,000,000
Holdings Count | Holding 120
InvestmentCompanyPortfolioTurnover 21.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$1,096
Number of portfolio holdings
120
Portfolio turnover rate
21%
C000233309  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Global Sustainable Equity Portfolio
Class Name Institutional Shares
Trading Symbol JHISX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Global Sustainable Equity Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Global Sustainable Equity Portfolio (Institutional Shares/JHISX)
$39
0.75%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 39
Expense Ratio, Percent 0.75% [11]
AssetsNet $ 13,000,000
Holdings Count | Holding 58
InvestmentCompanyPortfolioTurnover 49.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$13
Number of portfolio holdingsFootnote Reference#
58
Portfolio turnover rate
49%
FootnoteDescription
Footnote#
Does not include derivatives, except purchased options, if any.
C000233310  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Global Sustainable Equity Portfolio
Class Name Service Shares
No Trading Symbol [Flag] true
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Global Sustainable Equity Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Global Sustainable Equity Portfolio (Service Shares)
$46
0.87%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 46
Expense Ratio, Percent 0.87% [12]
AssetsNet $ 13,000,000
Holdings Count | Holding 58
InvestmentCompanyPortfolioTurnover 49.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$13
Number of portfolio holdingsFootnote Reference#
58
Portfolio turnover rate
49%
FootnoteDescription
Footnote#
Does not include derivatives, except purchased options, if any.
C000028742  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Global Technology and Innovation Portfolio
Class Name Institutional Shares
Trading Symbol JGLTX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Global Technology and Innovation Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Global Technology and Innovation Portfolio (Institutional Shares/JGLTX)
$42
0.72%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 42
Expense Ratio, Percent 0.72% [13]
AssetsNet $ 1,869,000,000
Holdings Count | Holding 53
InvestmentCompanyPortfolioTurnover 31.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$1,869
Number of portfolio holdings
53
Portfolio turnover rate
31%
C000028740  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Global Technology and Innovation Portfolio
Class Name Service Shares
No Trading Symbol [Flag] true
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Global Technology and Innovation Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Global Technology and Innovation Portfolio (Service Shares)
$56
0.97%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 56
Expense Ratio, Percent 0.97% [14]
AssetsNet $ 1,869,000,000
Holdings Count | Holding 53
InvestmentCompanyPortfolioTurnover 31.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$1,869
Number of portfolio holdings
53
Portfolio turnover rate
31%
C000028723  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Mid Cap Value Portfolio
Class Name Institutional Shares
Trading Symbol JAMVX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Mid Cap Value Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Mid Cap Value Portfolio (Institutional Shares/JAMVX)
$36
0.68%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 36
Expense Ratio, Percent 0.68% [15]
AssetsNet $ 123,000,000
Holdings Count | Holding 74
InvestmentCompanyPortfolioTurnover 20.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$123
Number of portfolio holdings
74
Portfolio turnover rate
20%
C000028722  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Mid Cap Value Portfolio
Class Name Service Shares
No Trading Symbol [Flag] true
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Mid Cap Value Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Mid Cap Value Portfolio (Service Shares)
$49
0.92%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 49
Expense Ratio, Percent 0.92% [16]
AssetsNet $ 123,000,000
Holdings Count | Holding 74
InvestmentCompanyPortfolioTurnover 20.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$123
Number of portfolio holdings
74
Portfolio turnover rate
20%
C000028747  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Overseas Portfolio
Class Name Institutional Shares
Trading Symbol JAIGX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Overseas Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Overseas Portfolio (Institutional Shares/JAIGX)
$33
0.61%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 33
Expense Ratio, Percent 0.61% [17]
AssetsNet $ 853,000,000
Holdings Count | Holding 46
InvestmentCompanyPortfolioTurnover 33.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$853
Number of portfolio holdings
46
Portfolio turnover rate
33%
C000028745  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Overseas Portfolio
Class Name Service Shares
No Trading Symbol [Flag] true
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Overseas Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Overseas Portfolio (Service Shares)
$45
0.85%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 45
Expense Ratio, Percent 0.85% [18]
AssetsNet $ 853,000,000
Holdings Count | Holding 46
InvestmentCompanyPortfolioTurnover 33.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$853
Number of portfolio holdings
46
Portfolio turnover rate
33%
C000028719  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Research Portfolio
Class Name Institutional Shares
Trading Symbol JAGRX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Research Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Research Portfolio (Institutional Shares/JAGRX)
$40
0.77%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 40
Expense Ratio, Percent 0.77% [19]
AssetsNet $ 784,000,000
Holdings Count | Holding 81
InvestmentCompanyPortfolioTurnover 27.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$784
Number of portfolio holdings
81
Portfolio turnover rate
27%
C000028718  
Shareholder Report [Line Items]  
Fund Name Janus Henderson VIT Research Portfolio
Class Name Service Shares
No Trading Symbol [Flag] true
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Janus Henderson VIT Research Portfolio (the "Portfolio") for the period of January 1, 2026 to June 30, 2026.
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
Additional Information [Text Block] You can find additional information about the Portfolio at janushenderson.com/VIT. You can also request this information by contacting us at 1-877-335-2687.
Additional Information Website janushenderson.com/VIT
Expenses [Text Block]

What were the costs for the last six months?

(Based on a hypothetical $10,000 investment)

Table Summary
Portfolio (Class)
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Janus Henderson VIT Research Portfolio (Service Shares)
$53
1.02%Footnote Reference*
FootnoteDescription
Footnote*
Annualized for periods of less than one full year.
Expenses Paid, Amount $ 53
Expense Ratio, Percent 1.02% [20]
AssetsNet $ 784,000,000
Holdings Count | Holding 81
InvestmentCompanyPortfolioTurnover 27.00%
Additional Fund Statistics [Text Block]

Key Portfolio Statistics

Table Summary
Net assets (Millions)
$784
Number of portfolio holdings
81
Portfolio turnover rate
27%
[1] Annualized for periods of less than one full year.
[2] Annualized for periods of less than one full year.
[3] Annualized for periods of less than one full year.
[4] Annualized for periods of less than one full year.
[5] Annualized for periods of less than one full year.
[6] Annualized for periods of less than one full year.
[7] Annualized for periods of less than one full year.
[8] Annualized for periods of less than one full year.
[9] Annualized for periods of less than one full year.
[10] Annualized for periods of less than one full year.
[11] Annualized for periods of less than one full year.
[12] Annualized for periods of less than one full year.
[13] Annualized for periods of less than one full year.
[14] Annualized for periods of less than one full year.
[15] Annualized for periods of less than one full year.
[16] Annualized for periods of less than one full year.
[17] Annualized for periods of less than one full year.
[18] Annualized for periods of less than one full year.
[19] Annualized for periods of less than one full year.
[20] Annualized for periods of less than one full year.