v3.26.1
Shareholder Report
6 Months Ended
Jun. 30, 2026
USD ($)
Holding
Shareholder Report [Line Items]  
Document Type N-CSR
Amendment Flag false
Registrant Name Baillie Gifford Institutional Trust                                    
Entity Central Index Key 0002087828
Entity Investment Company Type N-1A
Document Period End Date Jun. 30, 2026
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
C000269504  
Shareholder Report [Line Items]  
Fund Name Baillie Gifford Institutional Long Term Global Growth Fund
Class Name Class 2
No Trading Symbol [Flag] true
Annual or Semi-Annual Statement [Text Block] The semi-annual shareholder report contains important information about  Baillie Gifford Institutional Long Term Global Growth Fund (the "Fund") for the period of February 5, 2026 (commencement of operations) to June 30, 2026.
Additional Information [Text Block] You can find additional information about the Fund at www.bailliegifford.com/ltgg/TSR. You can also request this information by contacting us at +1-844-394-6127 or via email at northamericanvehiclesteam@bailliegifford.com.    
Additional Information Phone Number +1-844-394-6127
Additional Information Website www.bailliegifford.com/ltgg/TSR
Expenses [Text Block]

What were the Fund costs for the last six months? 

(based on a hypothetical $10,000 investment)

Table Summary
Class
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Class 2
$29Footnote Reference*
0.70%Footnote Reference**
FootnoteDescription
Footnote*
The period from commencement to the date of this report is less than a full reporting period. Expenses paid for a full reporting period would be higher.
Footnote**
Annualized
Expenses Paid, Amount $ 29 [1]
Expense Ratio, Percent 0.70% [2]
AssetsNet $ 138,236,652
Holdings Count | Holding 38
Advisory Fees Paid, Amount $ 210,944
InvestmentCompanyPortfolioTurnover 19.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics as of June 30, 2026

The following table outlines key Fund statistics that you should pay attention to:

  • Fund net assets$138,236,652
  • Total number of portfolio holdings38
  • Total advisory fees paid, net of waiver$210,944
  • Portfolio turnover rate19%
Additional Fund Statistics Significance or Limits [Text Block]

The following table outlines key Fund statistics that you should pay attention to:

Holdings [Text Block]

Tabular Representation of Holdings as of June 30, 2026

The following table shows the industry sector allocation of the Fund.

Table Summary
Sectors
% of Net Assets
Internet
35.6%
Semiconductors
21.8%
Software
10.3%
Auto Parts & Equipment
3.4%
Aerospace/Defense
3.1%
Banks
3.0%
Retail
2.8%
Miscellaneous Manufacturing
2.4%
Healthcare - Products
2.1%
Apparel
2.0%
Commercial Services
2.0%
Pharmaceuticals
1.9%
Biotechnology
1.9%
Other sectors
6.8%
Other assets less liabilities
0.9%
Total
100.0%
C000269505  
Shareholder Report [Line Items]  
Fund Name Baillie Gifford Institutional Long Term Global Growth Fund
Class Name Class 3
No Trading Symbol [Flag] true
Annual or Semi-Annual Statement [Text Block] The semi-annual shareholder report contains important information about  Baillie Gifford Institutional Long Term Global Growth Fund (the "Fund") for the period of February 5, 2026 (commencement of operations) to June 30, 2026.
Additional Information [Text Block] You can find additional information about the Fund at www.bailliegifford.com/ltgg/TSR. You can also request this information by contacting us at +1-844-394-6127 or via email at northamericanvehiclesteam@bailliegifford.com.    
Additional Information Phone Number +1-844-394-6127
Additional Information Website www.bailliegifford.com/ltgg/TSR
Expenses [Text Block]

What were the Fund costs for the last six months? 

(based on a hypothetical $10,000 investment)

Table Summary
Class
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Class 3
$26Footnote Reference*
0.63%Footnote Reference**
FootnoteDescription
Footnote*
The period from commencement to the date of this report is less than a full reporting period. Expenses paid for a full reporting period would be higher.
Footnote**
Annualized
Expenses Paid, Amount $ 26 [3]
Expense Ratio, Percent 0.63% [4]
AssetsNet $ 138,236,652
Holdings Count | Holding 38
Advisory Fees Paid, Amount $ 210,944
InvestmentCompanyPortfolioTurnover 19.00%
Additional Fund Statistics [Text Block]

Key Fund Statistics as of June 30, 2026

The following table outlines key Fund statistics that you should pay attention to:

  • Fund net assets$138,236,652
  • Total number of portfolio holdings38
  • Total advisory fees paid, net of waiver$210,944
  • Portfolio turnover rate19%
Additional Fund Statistics Significance or Limits [Text Block]

The following table outlines key Fund statistics that you should pay attention to:

Holdings [Text Block]

Tabular Representation of Holdings as of June 30, 2026

The following table shows the industry sector allocation of the Fund.

Table Summary
Sectors
% of Net Assets
Internet
35.6%
Semiconductors
21.8%
Software
10.3%
Auto Parts & Equipment
3.4%
Aerospace/Defense
3.1%
Banks
3.0%
Retail
2.8%
Miscellaneous Manufacturing
2.4%
Healthcare - Products
2.1%
Apparel
2.0%
Commercial Services
2.0%
Pharmaceuticals
1.9%
Biotechnology
1.9%
Other sectors
6.8%
Other assets less liabilities
0.9%
Total
100.0%
[1] The period from commencement to the date of this report is less than a full reporting period. Expenses paid for a full reporting period would be higher.
[2] Annualized
[3] The period from commencement to the date of this report is less than a full reporting period. Expenses paid for a full reporting period would be higher.
[4] Annualized